feat(dcr): Add Redis storage support for multi-replica deployments (#109)

- [x] Add file and Redis storage backends for DCR credentials
- [x] Implement storage abstraction with FileStore and RedisStore
- [x] Add factory function for automatic backend selection (auto/file/redis)
- [x] Integrate DCR credentials cache into UniversalCacheManager
- [x] Add comprehensive tests for storage backends and factory
- [x] Update configuration schema with storage backend options
- [x] Update documentation with multi-replica deployment guidance
- [x] Add Redis key prefix configuration for credential isolation

.traefik.yml

@@ -1630,3 +1630,234 @@ configuration:
 
           Default: 30 seconds
         required: false
+
+  dynamicClientRegistration:
+    type: object
+    description: |
+      Configuration for OIDC Dynamic Client Registration (RFC 7591/7592).
+
+      Dynamic Client Registration allows the middleware to automatically register
+      itself as an OAuth 2.0 client with the OIDC provider, eliminating the need
+      to manually create and manage client credentials.
+
+      This is particularly useful for:
+      - Automated deployments where manual client creation is impractical
+      - Multi-tenant scenarios requiring per-deployment client isolation
+      - Development and testing environments
+      - Kubernetes environments with multiple replicas
+
+      For multi-replica deployments (Kubernetes), enable Redis storage to share
+      credentials across all instances and prevent registration race conditions.
+
+      Example configuration:
+      ```yaml
+      dynamicClientRegistration:
+        enabled: true
+        persistCredentials: true
+        storageBackend: "redis"  # Use Redis for distributed storage
+        clientMetadata:
+          redirect_uris:
+            - https://app.example.com/oauth2/callback
+          client_name: "My Application"
+          application_type: "web"
+      ```
+    required: false
+    properties:
+      enabled:
+        type: boolean
+        description: |
+          Enable dynamic client registration with the OIDC provider.
+          When enabled and clientID is not set, the middleware will automatically
+          register itself with the provider using the configuration in clientMetadata.
+
+          Default: false
+        required: false
+
+      persistCredentials:
+        type: boolean
+        description: |
+          Enable persistence of client credentials after registration.
+          When enabled, credentials are saved to the configured storage backend
+          and reloaded on restart to avoid re-registration.
+
+          Default: false
+        required: false
+
+      storageBackend:
+        type: string
+        description: |
+          Storage backend for persisting DCR credentials.
+
+          Options:
+          - "file": Store credentials in a local file (default for backward compatibility)
+          - "redis": Store credentials in Redis (recommended for multi-replica deployments)
+          - "auto": Use Redis if available, fall back to file storage
+
+          For Kubernetes deployments with multiple replicas, use "redis" to ensure
+          all instances share the same client credentials and prevent registration
+          race conditions where each replica registers its own client.
+
+          Default: "auto"
+        required: false
+        enum:
+          - file
+          - redis
+          - auto
+
+      credentialsFile:
+        type: string
+        description: |
+          Path to store client credentials when using file-based storage.
+          The file will be created with restrictive permissions (0600).
+
+          Default: "/tmp/oidc-client-credentials.json"
+        required: false
+
+      redisKeyPrefix:
+        type: string
+        description: |
+          Prefix for Redis keys when using Redis storage.
+          Useful for isolating credentials between different applications
+          or environments sharing the same Redis instance.
+
+          Default: "dcr:creds:"
+        required: false
+
+      registrationEndpoint:
+        type: string
+        description: |
+          Override the registration endpoint URL.
+          If not specified, the endpoint will be discovered from provider metadata.
+
+          Some providers may not advertise their registration endpoint in metadata,
+          in which case you need to specify it explicitly.
+
+          Example: "https://auth.example.com/oauth/register"
+        required: false
+
+      initialAccessToken:
+        type: string
+        description: |
+          Initial Access Token for protected registration endpoints.
+          Some providers require an access token to authorize client registration.
+
+          If your provider requires authentication for registration, obtain an
+          initial access token from the provider and configure it here.
+
+          For Kubernetes, you can use secret references:
+          urn:k8s:secret:namespace:secret-name:key
+        required: false
+
+      clientMetadata:
+        type: object
+        description: |
+          Client metadata to include in the registration request (RFC 7591).
+          This defines the properties of the OAuth 2.0 client to be registered.
+        required: false
+        properties:
+          redirect_uris:
+            type: array
+            description: |
+              Array of redirect URIs for the client. Required for registration.
+              These must match the callback URLs that will be used in authentication flows.
+
+              Example: ["https://app.example.com/oauth2/callback"]
+            required: true
+            items:
+              type: string
+
+          client_name:
+            type: string
+            description: |
+              Human-readable name of the client.
+              This is typically displayed in consent screens.
+
+              Example: "My Application"
+            required: false
+
+          application_type:
+            type: string
+            description: |
+              Type of application. Affects security defaults.
+
+              Options:
+              - "web": Server-side web application (default)
+              - "native": Native/mobile application
+
+              Default: "web"
+            required: false
+
+          grant_types:
+            type: array
+            description: |
+              OAuth 2.0 grant types the client will use.
+
+              Default: ["authorization_code", "refresh_token"]
+            required: false
+            items:
+              type: string
+
+          response_types:
+            type: array
+            description: |
+              OAuth 2.0 response types the client will use.
+
+              Default: ["code"]
+            required: false
+            items:
+              type: string
+
+          token_endpoint_auth_method:
+            type: string
+            description: |
+              Authentication method for the token endpoint.
+
+              Options:
+              - "client_secret_basic": HTTP Basic authentication (default)
+              - "client_secret_post": Client credentials in POST body
+              - "none": Public client (no authentication)
+
+              Default: "client_secret_basic"
+            required: false
+
+          scope:
+            type: string
+            description: |
+              Space-separated list of scopes the client is authorized to request.
+
+              Example: "openid profile email"
+            required: false
+
+          contacts:
+            type: array
+            description: |
+              Array of contact email addresses for the client administrator.
+
+              Example: ["admin@example.com"]
+            required: false
+            items:
+              type: string
+
+          logo_uri:
+            type: string
+            description: |
+              URL to the client's logo image for consent screens.
+            required: false
+
+          client_uri:
+            type: string
+            description: |
+              URL to the client's home page.
+            required: false
+
+          policy_uri:
+            type: string
+            description: |
+              URL to the client's privacy policy.
+            required: false
+
+          tos_uri:
+            type: string
+            description: |
+              URL to the client's terms of service.
+            required: false

README.md

@@ -8,7 +8,7 @@ The Traefik OIDC middleware provides a complete OIDC authentication solution wit
 
 - **Universal provider support**: Works with 9+ OIDC providers including Google, Azure AD, Auth0, Okta, Keycloak, AWS Cognito, GitLab, and more
 - **Automatic provider detection**: Automatically detects and configures provider-specific settings
-- **Dynamic Client Registration (RFC 7591)**: Automatic client registration with OIDC providers without manual pre-registration
+- **Dynamic Client Registration (RFC 7591)**: Automatic client registration with OIDC providers without manual pre-registration, with Redis storage support for multi-replica deployments
 - **Automatic scope filtering**: Intelligently filters OAuth scopes based on provider capabilities declared in OIDC discovery documents, preventing authentication failures with unsupported scopes
 - **Security headers**: Comprehensive security headers with CORS, CSP, HSTS, and custom profiles
 - **Domain restrictions**: Limit access to specific email domains or individual users

dcr_storage_compat.go

@@ -0,0 +1,290 @@
+// Package traefikoidc provides OIDC authentication middleware for Traefik
+package traefikoidc
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/lukaszraczylo/traefikoidc/internal/dcrstorage"
+)
+
+// DCRStorageBackend represents the type of storage backend for DCR credentials.
+// Alias for internal package type for backward compatibility.
+type DCRStorageBackend = dcrstorage.StorageBackend
+
+const (
+	// DCRStorageBackendFile uses file-based storage (default for backward compatibility)
+	DCRStorageBackendFile DCRStorageBackend = dcrstorage.StorageBackendFile
+
+	// DCRStorageBackendRedis uses Redis for distributed storage
+	DCRStorageBackendRedis DCRStorageBackend = dcrstorage.StorageBackendRedis
+
+	// DCRStorageBackendAuto automatically selects Redis if available, otherwise file
+	DCRStorageBackendAuto DCRStorageBackend = dcrstorage.StorageBackendAuto
+)
+
+// DCRCredentialsStore defines the interface for storing DCR credentials.
+// This abstraction allows different storage backends (file, Redis) to be used
+// for persisting OIDC Dynamic Client Registration credentials across nodes.
+type DCRCredentialsStore interface {
+	// Save stores the client registration response for a provider
+	// The providerURL is used as a key to support multi-tenant scenarios
+	Save(ctx context.Context, providerURL string, creds *ClientRegistrationResponse) error
+
+	// Load retrieves stored credentials for a provider
+	// Returns nil, nil if no credentials exist (not an error)
+	Load(ctx context.Context, providerURL string) (*ClientRegistrationResponse, error)
+
+	// Delete removes stored credentials for a provider
+	Delete(ctx context.Context, providerURL string) error
+
+	// Exists checks if credentials exist for a provider
+	Exists(ctx context.Context, providerURL string) (bool, error)
+}
+
+// loggerAdapter adapts our Logger to the dcrstorage.Logger interface
+type loggerAdapter struct {
+	logger *Logger
+}
+
+func (l *loggerAdapter) Debug(msg string)                  { l.logger.Debug("%s", msg) }
+func (l *loggerAdapter) Debugf(format string, args ...any) { l.logger.Debugf(format, args...) }
+func (l *loggerAdapter) Info(msg string)                   { l.logger.Info("%s", msg) }
+func (l *loggerAdapter) Infof(format string, args ...any)  { l.logger.Infof(format, args...) }
+func (l *loggerAdapter) Error(msg string)                  { l.logger.Error("%s", msg) }
+func (l *loggerAdapter) Errorf(format string, args ...any) { l.logger.Errorf(format, args...) }
+
+// cacheAdapter adapts UniversalCache to dcrstorage.Cache interface
+type cacheAdapter struct {
+	cache *UniversalCache
+}
+
+func (c *cacheAdapter) Get(key string) (any, bool) {
+	return c.cache.Get(key)
+}
+
+func (c *cacheAdapter) Set(key string, value any, ttl time.Duration) error {
+	return c.cache.Set(key, value, ttl)
+}
+
+func (c *cacheAdapter) Delete(key string) {
+	c.cache.Delete(key)
+}
+
+// fileStoreWrapper wraps dcrstorage.FileStore to implement DCRCredentialsStore
+type fileStoreWrapper struct {
+	inner *dcrstorage.FileStore
+}
+
+func (w *fileStoreWrapper) Save(ctx context.Context, providerURL string, creds *ClientRegistrationResponse) error {
+	innerCreds := convertCredsToInternal(creds)
+	return w.inner.Save(ctx, providerURL, innerCreds)
+}
+
+func (w *fileStoreWrapper) Load(ctx context.Context, providerURL string) (*ClientRegistrationResponse, error) {
+	innerCreds, err := w.inner.Load(ctx, providerURL)
+	if err != nil || innerCreds == nil {
+		return nil, err
+	}
+	return convertCredsFromInternal(innerCreds), nil
+}
+
+func (w *fileStoreWrapper) Delete(ctx context.Context, providerURL string) error {
+	return w.inner.Delete(ctx, providerURL)
+}
+
+func (w *fileStoreWrapper) Exists(ctx context.Context, providerURL string) (bool, error) {
+	return w.inner.Exists(ctx, providerURL)
+}
+
+// basePath returns the base path used for storing credentials (for backward compatibility in tests)
+func (w *fileStoreWrapper) basePath() string {
+	return w.inner.BasePath()
+}
+
+// getFilePath returns the file path for storing credentials for a specific provider (for backward compatibility in tests)
+func (w *fileStoreWrapper) getFilePath(providerURL string) string {
+	return w.inner.GetFilePath(providerURL)
+}
+
+// redisStoreWrapper wraps dcrstorage.RedisStore to implement DCRCredentialsStore
+type redisStoreWrapper struct {
+	inner *dcrstorage.RedisStore
+}
+
+func (w *redisStoreWrapper) Save(ctx context.Context, providerURL string, creds *ClientRegistrationResponse) error {
+	innerCreds := convertCredsToInternal(creds)
+	return w.inner.Save(ctx, providerURL, innerCreds)
+}
+
+func (w *redisStoreWrapper) Load(ctx context.Context, providerURL string) (*ClientRegistrationResponse, error) {
+	innerCreds, err := w.inner.Load(ctx, providerURL)
+	if err != nil || innerCreds == nil {
+		return nil, err
+	}
+	return convertCredsFromInternal(innerCreds), nil
+}
+
+func (w *redisStoreWrapper) Delete(ctx context.Context, providerURL string) error {
+	return w.inner.Delete(ctx, providerURL)
+}
+
+func (w *redisStoreWrapper) Exists(ctx context.Context, providerURL string) (bool, error) {
+	return w.inner.Exists(ctx, providerURL)
+}
+
+// FileCredentialsStore implements DCRCredentialsStore using file-based storage.
+// This is the default storage backend for backward compatibility with existing deployments.
+type FileCredentialsStore = fileStoreWrapper
+
+// RedisCredentialsStore implements DCRCredentialsStore using Redis-backed cache.
+// This storage backend enables sharing DCR credentials across multiple Traefik instances.
+type RedisCredentialsStore = redisStoreWrapper
+
+// NewFileCredentialsStore creates a new file-based credentials store.
+// If basePath is empty, defaults to /tmp/oidc-client-credentials.json
+func NewFileCredentialsStore(basePath string, logger *Logger) *FileCredentialsStore {
+	var dcrLogger dcrstorage.Logger
+	if logger != nil {
+		dcrLogger = &loggerAdapter{logger: logger}
+	}
+	inner := dcrstorage.NewFileStore(basePath, dcrLogger)
+	return &fileStoreWrapper{inner: inner}
+}
+
+// NewRedisCredentialsStore creates a new Redis-backed credentials store.
+// The cache should be configured with a Redis backend for distributed storage.
+// If keyPrefix is empty, defaults to "dcr:creds:"
+func NewRedisCredentialsStore(cache *UniversalCache, keyPrefix string, logger *Logger) *RedisCredentialsStore {
+	var dcrLogger dcrstorage.Logger
+	if logger != nil {
+		dcrLogger = &loggerAdapter{logger: logger}
+	}
+	cacheAdapt := &cacheAdapter{cache: cache}
+	inner := dcrstorage.NewRedisStore(cacheAdapt, keyPrefix, dcrLogger)
+	return &redisStoreWrapper{inner: inner}
+}
+
+// Helper functions to convert between main package and internal package types
+func convertCredsToInternal(creds *ClientRegistrationResponse) *dcrstorage.ClientRegistrationResponse {
+	if creds == nil {
+		return nil
+	}
+	return &dcrstorage.ClientRegistrationResponse{
+		SubjectType:             creds.SubjectType,
+		LogoURI:                 creds.LogoURI,
+		RegistrationAccessToken: creds.RegistrationAccessToken,
+		RegistrationClientURI:   creds.RegistrationClientURI,
+		Scope:                   creds.Scope,
+		TokenEndpointAuthMethod: creds.TokenEndpointAuthMethod,
+		TOSURI:                  creds.TOSURI,
+		PolicyURI:               creds.PolicyURI,
+		ClientSecret:            creds.ClientSecret,
+		ApplicationType:         creds.ApplicationType,
+		ClientID:                creds.ClientID,
+		ClientName:              creds.ClientName,
+		JWKSURI:                 creds.JWKSURI,
+		ClientURI:               creds.ClientURI,
+		Contacts:                creds.Contacts,
+		GrantTypes:              creds.GrantTypes,
+		ResponseTypes:           creds.ResponseTypes,
+		RedirectURIs:            creds.RedirectURIs,
+		ClientSecretExpiresAt:   creds.ClientSecretExpiresAt,
+		ClientIDIssuedAt:        creds.ClientIDIssuedAt,
+	}
+}
+
+func convertCredsFromInternal(creds *dcrstorage.ClientRegistrationResponse) *ClientRegistrationResponse {
+	if creds == nil {
+		return nil
+	}
+	return &ClientRegistrationResponse{
+		SubjectType:             creds.SubjectType,
+		LogoURI:                 creds.LogoURI,
+		RegistrationAccessToken: creds.RegistrationAccessToken,
+		RegistrationClientURI:   creds.RegistrationClientURI,
+		Scope:                   creds.Scope,
+		TokenEndpointAuthMethod: creds.TokenEndpointAuthMethod,
+		TOSURI:                  creds.TOSURI,
+		PolicyURI:               creds.PolicyURI,
+		ClientSecret:            creds.ClientSecret,
+		ApplicationType:         creds.ApplicationType,
+		ClientID:                creds.ClientID,
+		ClientName:              creds.ClientName,
+		JWKSURI:                 creds.JWKSURI,
+		ClientURI:               creds.ClientURI,
+		Contacts:                creds.Contacts,
+		GrantTypes:              creds.GrantTypes,
+		ResponseTypes:           creds.ResponseTypes,
+		RedirectURIs:            creds.RedirectURIs,
+		ClientSecretExpiresAt:   creds.ClientSecretExpiresAt,
+		ClientIDIssuedAt:        creds.ClientIDIssuedAt,
+	}
+}
+
+// NewDCRCredentialsStore creates a DCRCredentialsStore based on configuration.
+// This factory function handles backend selection logic:
+//   - "file": Use file-based storage (default for backward compatibility)
+//   - "redis": Use Redis exclusively (fails if Redis unavailable)
+//   - "auto": Use Redis if available, fallback to file
+func NewDCRCredentialsStore(
+	config *DynamicClientRegistrationConfig,
+	cacheManager *CacheManager,
+	logger *Logger,
+) (DCRCredentialsStore, error) {
+	if config == nil {
+		return nil, fmt.Errorf("DCR config is nil")
+	}
+
+	if logger == nil {
+		logger = GetSingletonNoOpLogger()
+	}
+
+	backend := config.StorageBackend
+	if backend == "" {
+		backend = string(DCRStorageBackendAuto) // Default to auto selection
+	}
+
+	switch DCRStorageBackend(backend) {
+	case DCRStorageBackendFile:
+		logger.Info("Using file-based storage for DCR credentials")
+		return NewFileCredentialsStore(config.CredentialsFile, logger), nil
+
+	case DCRStorageBackendRedis:
+		cache := getDCRCache(cacheManager)
+		if cache == nil {
+			return nil, fmt.Errorf("redis storage requested but Redis/cache not configured")
+		}
+		logger.Info("Using Redis storage for DCR credentials")
+		return NewRedisCredentialsStore(cache, config.RedisKeyPrefix, logger), nil
+
+	case DCRStorageBackendAuto:
+		// Try Redis first, fallback to file
+		cache := getDCRCache(cacheManager)
+		if cache != nil && cache.backend != nil {
+			logger.Info("Auto-selected Redis storage for DCR credentials")
+			return NewRedisCredentialsStore(cache, config.RedisKeyPrefix, logger), nil
+		}
+		logger.Info("Redis not available, using file storage for DCR credentials")
+		return NewFileCredentialsStore(config.CredentialsFile, logger), nil
+
+	default:
+		return nil, fmt.Errorf("unknown DCR storage backend: %s", backend)
+	}
+}
+
+// getDCRCache safely retrieves the DCR credentials cache from the cache manager
+func getDCRCache(cacheManager *CacheManager) *UniversalCache {
+	if cacheManager == nil {
+		return nil
+	}
+	cacheManager.mu.RLock()
+	defer cacheManager.mu.RUnlock()
+
+	if cacheManager.manager == nil {
+		return nil
+	}
+
+	return cacheManager.manager.GetDCRCredentialsCache()
+}

dcr_storage_test.go

@@ -0,0 +1,663 @@
+// Package traefikoidc provides OIDC authentication middleware for Traefik
+package traefikoidc
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"sync"
+	"testing"
+	"time"
+)
+
+// TestFileCredentialsStore_SaveLoad tests the file-based credentials store
+func TestFileCredentialsStore_SaveLoad(t *testing.T) {
+	t.Parallel()
+
+	// Create a temp directory for test files
+	tempDir := t.TempDir()
+	basePath := filepath.Join(tempDir, "credentials.json")
+
+	logger := GetSingletonNoOpLogger()
+	store := NewFileCredentialsStore(basePath, logger)
+
+	testCreds := &ClientRegistrationResponse{
+		ClientID:                "test-client-id",
+		ClientSecret:            "test-client-secret",
+		ClientSecretExpiresAt:   time.Now().Add(24 * time.Hour).Unix(),
+		RegistrationAccessToken: "test-access-token",
+		RegistrationClientURI:   "https://example.com/register/test-client-id",
+		RedirectURIs:            []string{"https://app.example.com/callback"},
+		GrantTypes:              []string{"authorization_code", "refresh_token"},
+		ResponseTypes:           []string{"code"},
+		TokenEndpointAuthMethod: "client_secret_basic",
+	}
+
+	ctx := context.Background()
+	providerURL := "https://auth.example.com"
+
+	t.Run("save and load credentials", func(t *testing.T) {
+		// Save credentials
+		err := store.Save(ctx, providerURL, testCreds)
+		if err != nil {
+			t.Fatalf("Failed to save credentials: %v", err)
+		}
+
+		// Load credentials
+		loaded, err := store.Load(ctx, providerURL)
+		if err != nil {
+			t.Fatalf("Failed to load credentials: %v", err)
+		}
+
+		if loaded == nil {
+			t.Fatal("Expected credentials but got nil")
+		}
+
+		// Verify fields
+		if loaded.ClientID != testCreds.ClientID {
+			t.Errorf("ClientID mismatch: got %s, want %s", loaded.ClientID, testCreds.ClientID)
+		}
+		if loaded.ClientSecret != testCreds.ClientSecret {
+			t.Errorf("ClientSecret mismatch: got %s, want %s", loaded.ClientSecret, testCreds.ClientSecret)
+		}
+		if loaded.RegistrationAccessToken != testCreds.RegistrationAccessToken {
+			t.Errorf("RegistrationAccessToken mismatch: got %s, want %s", loaded.RegistrationAccessToken, testCreds.RegistrationAccessToken)
+		}
+	})
+
+	t.Run("load non-existent credentials", func(t *testing.T) {
+		tempDir2 := t.TempDir()
+		store2 := NewFileCredentialsStore(filepath.Join(tempDir2, "nonexistent.json"), logger)
+
+		loaded, err := store2.Load(ctx, "https://nonexistent.example.com")
+		if err != nil {
+			t.Fatalf("Unexpected error for non-existent file: %v", err)
+		}
+		if loaded != nil {
+			t.Error("Expected nil for non-existent credentials")
+		}
+	})
+
+	t.Run("exists check", func(t *testing.T) {
+		exists, err := store.Exists(ctx, providerURL)
+		if err != nil {
+			t.Fatalf("Exists check failed: %v", err)
+		}
+		if !exists {
+			t.Error("Expected credentials to exist")
+		}
+
+		exists, err = store.Exists(ctx, "https://nonexistent.example.com")
+		if err != nil {
+			t.Fatalf("Exists check failed: %v", err)
+		}
+		if exists {
+			t.Error("Expected credentials to not exist")
+		}
+	})
+
+	t.Run("delete credentials", func(t *testing.T) {
+		err := store.Delete(ctx, providerURL)
+		if err != nil {
+			t.Fatalf("Failed to delete credentials: %v", err)
+		}
+
+		exists, _ := store.Exists(ctx, providerURL)
+		if exists {
+			t.Error("Expected credentials to be deleted")
+		}
+	})
+
+	t.Run("delete non-existent credentials", func(t *testing.T) {
+		// Should not error
+		err := store.Delete(ctx, "https://nonexistent.example.com")
+		if err != nil {
+			t.Fatalf("Delete should not error for non-existent: %v", err)
+		}
+	})
+}
+
+// TestFileCredentialsStore_MultiProvider tests multi-provider support
+func TestFileCredentialsStore_MultiProvider(t *testing.T) {
+	t.Parallel()
+
+	tempDir := t.TempDir()
+	basePath := filepath.Join(tempDir, "credentials.json")
+	logger := GetSingletonNoOpLogger()
+	store := NewFileCredentialsStore(basePath, logger)
+
+	ctx := context.Background()
+
+	provider1 := "https://auth1.example.com"
+	provider2 := "https://auth2.example.com"
+
+	creds1 := &ClientRegistrationResponse{
+		ClientID:     "client-1",
+		ClientSecret: "secret-1",
+	}
+	creds2 := &ClientRegistrationResponse{
+		ClientID:     "client-2",
+		ClientSecret: "secret-2",
+	}
+
+	// Save credentials for both providers
+	if err := store.Save(ctx, provider1, creds1); err != nil {
+		t.Fatalf("Failed to save creds1: %v", err)
+	}
+	if err := store.Save(ctx, provider2, creds2); err != nil {
+		t.Fatalf("Failed to save creds2: %v", err)
+	}
+
+	// Load and verify each provider's credentials
+	loaded1, err := store.Load(ctx, provider1)
+	if err != nil {
+		t.Fatalf("Failed to load creds1: %v", err)
+	}
+	if loaded1.ClientID != "client-1" {
+		t.Errorf("Provider 1 ClientID mismatch: got %s", loaded1.ClientID)
+	}
+
+	loaded2, err := store.Load(ctx, provider2)
+	if err != nil {
+		t.Fatalf("Failed to load creds2: %v", err)
+	}
+	if loaded2.ClientID != "client-2" {
+		t.Errorf("Provider 2 ClientID mismatch: got %s", loaded2.ClientID)
+	}
+
+	// Delete one shouldn't affect the other
+	if err := store.Delete(ctx, provider1); err != nil {
+		t.Fatalf("Failed to delete creds1: %v", err)
+	}
+
+	exists, _ := store.Exists(ctx, provider2)
+	if !exists {
+		t.Error("Provider 2 credentials should still exist")
+	}
+}
+
+// TestFileCredentialsStore_ConcurrentAccess tests thread safety
+func TestFileCredentialsStore_ConcurrentAccess(t *testing.T) {
+	t.Parallel()
+
+	tempDir := t.TempDir()
+	basePath := filepath.Join(tempDir, "credentials.json")
+	logger := GetSingletonNoOpLogger()
+	store := NewFileCredentialsStore(basePath, logger)
+
+	ctx := context.Background()
+	providerURL := "https://auth.example.com"
+
+	creds := &ClientRegistrationResponse{
+		ClientID:     "test-client",
+		ClientSecret: "test-secret",
+	}
+
+	var wg sync.WaitGroup
+	concurrency := 10
+
+	// Concurrent saves
+	for i := 0; i < concurrency; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			_ = store.Save(ctx, providerURL, creds)
+		}()
+	}
+	wg.Wait()
+
+	// Concurrent loads
+	for i := 0; i < concurrency; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			_, _ = store.Load(ctx, providerURL)
+		}()
+	}
+	wg.Wait()
+
+	// Final verification
+	loaded, err := store.Load(ctx, providerURL)
+	if err != nil {
+		t.Fatalf("Failed to load after concurrent access: %v", err)
+	}
+	if loaded == nil || loaded.ClientID != "test-client" {
+		t.Error("Credentials corrupted after concurrent access")
+	}
+}
+
+// TestFileCredentialsStore_InvalidInput tests error handling
+func TestFileCredentialsStore_InvalidInput(t *testing.T) {
+	t.Parallel()
+
+	tempDir := t.TempDir()
+	basePath := filepath.Join(tempDir, "credentials.json")
+	logger := GetSingletonNoOpLogger()
+	store := NewFileCredentialsStore(basePath, logger)
+
+	ctx := context.Background()
+
+	t.Run("save nil credentials", func(t *testing.T) {
+		err := store.Save(ctx, "https://example.com", nil)
+		if err == nil {
+			t.Error("Expected error for nil credentials")
+		}
+	})
+
+	t.Run("empty provider URL uses default path", func(t *testing.T) {
+		creds := &ClientRegistrationResponse{ClientID: "test"}
+		err := store.Save(ctx, "", creds)
+		if err != nil {
+			t.Fatalf("Save with empty provider URL failed: %v", err)
+		}
+
+		loaded, err := store.Load(ctx, "")
+		if err != nil {
+			t.Fatalf("Load with empty provider URL failed: %v", err)
+		}
+		if loaded == nil || loaded.ClientID != "test" {
+			t.Error("Failed to load credentials with empty provider URL")
+		}
+	})
+}
+
+// TestFileCredentialsStore_DefaultPath tests default path behavior
+func TestFileCredentialsStore_DefaultPath(t *testing.T) {
+	t.Parallel()
+
+	logger := GetSingletonNoOpLogger()
+	store := NewFileCredentialsStore("", logger)
+
+	// Just verify we can create with empty path and it has a default
+	if store.basePath() == "" {
+		t.Error("Expected default base path")
+	}
+}
+
+// TestRedisCredentialsStore_WithMemoryCache tests Redis store with in-memory cache
+func TestRedisCredentialsStore_WithMemoryCache(t *testing.T) {
+	t.Parallel()
+
+	// Create an in-memory cache for testing
+	cache := NewUniversalCache(UniversalCacheConfig{
+		Type:       CacheTypeGeneral,
+		MaxSize:    100,
+		DefaultTTL: time.Hour,
+		Logger:     GetSingletonNoOpLogger(),
+	})
+	defer cache.Close()
+
+	logger := GetSingletonNoOpLogger()
+	store := NewRedisCredentialsStore(cache, "", logger)
+
+	ctx := context.Background()
+	providerURL := "https://auth.example.com"
+
+	testCreds := &ClientRegistrationResponse{
+		ClientID:                "redis-test-client",
+		ClientSecret:            "redis-test-secret",
+		ClientSecretExpiresAt:   time.Now().Add(24 * time.Hour).Unix(),
+		RegistrationAccessToken: "redis-test-token",
+		RedirectURIs:            []string{"https://app.example.com/callback"},
+	}
+
+	t.Run("save and load credentials", func(t *testing.T) {
+		err := store.Save(ctx, providerURL, testCreds)
+		if err != nil {
+			t.Fatalf("Failed to save credentials: %v", err)
+		}
+
+		loaded, err := store.Load(ctx, providerURL)
+		if err != nil {
+			t.Fatalf("Failed to load credentials: %v", err)
+		}
+
+		if loaded == nil {
+			t.Fatal("Expected credentials but got nil")
+		}
+		if loaded.ClientID != testCreds.ClientID {
+			t.Errorf("ClientID mismatch: got %s, want %s", loaded.ClientID, testCreds.ClientID)
+		}
+		if loaded.ClientSecret != testCreds.ClientSecret {
+			t.Errorf("ClientSecret mismatch: got %s, want %s", loaded.ClientSecret, testCreds.ClientSecret)
+		}
+	})
+
+	t.Run("exists check", func(t *testing.T) {
+		exists, err := store.Exists(ctx, providerURL)
+		if err != nil {
+			t.Fatalf("Exists check failed: %v", err)
+		}
+		if !exists {
+			t.Error("Expected credentials to exist")
+		}
+	})
+
+	t.Run("delete credentials", func(t *testing.T) {
+		err := store.Delete(ctx, providerURL)
+		if err != nil {
+			t.Fatalf("Failed to delete credentials: %v", err)
+		}
+
+		exists, _ := store.Exists(ctx, providerURL)
+		if exists {
+			t.Error("Expected credentials to be deleted")
+		}
+	})
+
+	t.Run("load non-existent credentials", func(t *testing.T) {
+		loaded, err := store.Load(ctx, "https://nonexistent.example.com")
+		if err != nil {
+			t.Fatalf("Unexpected error for non-existent: %v", err)
+		}
+		if loaded != nil {
+			t.Error("Expected nil for non-existent credentials")
+		}
+	})
+}
+
+// TestRedisCredentialsStore_TTLFromExpiry tests TTL calculation
+func TestRedisCredentialsStore_TTLFromExpiry(t *testing.T) {
+	t.Parallel()
+
+	cache := NewUniversalCache(UniversalCacheConfig{
+		Type:       CacheTypeGeneral,
+		MaxSize:    100,
+		DefaultTTL: time.Hour,
+		Logger:     GetSingletonNoOpLogger(),
+	})
+	defer cache.Close()
+
+	logger := GetSingletonNoOpLogger()
+	store := NewRedisCredentialsStore(cache, "", logger)
+
+	ctx := context.Background()
+
+	t.Run("expired credentials should fail", func(t *testing.T) {
+		expiredCreds := &ClientRegistrationResponse{
+			ClientID:              "expired-client",
+			ClientSecret:          "expired-secret",
+			ClientSecretExpiresAt: time.Now().Add(-1 * time.Hour).Unix(), // Already expired
+		}
+
+		err := store.Save(ctx, "https://expired.example.com", expiredCreds)
+		if err == nil {
+			t.Error("Expected error for expired credentials")
+		}
+	})
+
+	t.Run("credentials without expiry use default TTL", func(t *testing.T) {
+		creds := &ClientRegistrationResponse{
+			ClientID:              "no-expiry-client",
+			ClientSecret:          "no-expiry-secret",
+			ClientSecretExpiresAt: 0, // No expiry
+		}
+
+		err := store.Save(ctx, "https://noexpiry.example.com", creds)
+		if err != nil {
+			t.Fatalf("Failed to save credentials without expiry: %v", err)
+		}
+	})
+}
+
+// TestRedisCredentialsStore_InvalidInput tests error handling
+func TestRedisCredentialsStore_InvalidInput(t *testing.T) {
+	t.Parallel()
+
+	cache := NewUniversalCache(UniversalCacheConfig{
+		Type:       CacheTypeGeneral,
+		MaxSize:    100,
+		DefaultTTL: time.Hour,
+		Logger:     GetSingletonNoOpLogger(),
+	})
+	defer cache.Close()
+
+	logger := GetSingletonNoOpLogger()
+	store := NewRedisCredentialsStore(cache, "", logger)
+
+	ctx := context.Background()
+
+	t.Run("save nil credentials", func(t *testing.T) {
+		err := store.Save(ctx, "https://example.com", nil)
+		if err == nil {
+			t.Error("Expected error for nil credentials")
+		}
+	})
+}
+
+// TestDCRStorageFactory tests the factory function
+func TestDCRStorageFactory(t *testing.T) {
+	t.Parallel()
+
+	logger := GetSingletonNoOpLogger()
+
+	t.Run("nil config returns error", func(t *testing.T) {
+		_, err := NewDCRCredentialsStore(nil, nil, logger)
+		if err == nil {
+			t.Error("Expected error for nil config")
+		}
+	})
+
+	t.Run("file backend creates file store", func(t *testing.T) {
+		config := &DynamicClientRegistrationConfig{
+			Enabled:            true,
+			PersistCredentials: true,
+			StorageBackend:     "file",
+			CredentialsFile:    "/tmp/test-creds.json",
+		}
+
+		store, err := NewDCRCredentialsStore(config, nil, logger)
+		if err != nil {
+			t.Fatalf("Failed to create file store: %v", err)
+		}
+		if store == nil {
+			t.Error("Expected store but got nil")
+		}
+
+		_, ok := store.(*FileCredentialsStore)
+		if !ok {
+			t.Error("Expected FileCredentialsStore")
+		}
+	})
+
+	t.Run("redis backend without cache manager returns error", func(t *testing.T) {
+		config := &DynamicClientRegistrationConfig{
+			Enabled:            true,
+			PersistCredentials: true,
+			StorageBackend:     "redis",
+		}
+
+		_, err := NewDCRCredentialsStore(config, nil, logger)
+		if err == nil {
+			t.Error("Expected error for redis backend without cache manager")
+		}
+	})
+
+	t.Run("auto backend without redis falls back to file", func(t *testing.T) {
+		config := &DynamicClientRegistrationConfig{
+			Enabled:            true,
+			PersistCredentials: true,
+			StorageBackend:     "auto",
+		}
+
+		store, err := NewDCRCredentialsStore(config, nil, logger)
+		if err != nil {
+			t.Fatalf("Failed to create auto store: %v", err)
+		}
+
+		_, ok := store.(*FileCredentialsStore)
+		if !ok {
+			t.Error("Expected FileCredentialsStore for auto without redis")
+		}
+	})
+
+	t.Run("unknown backend returns error", func(t *testing.T) {
+		config := &DynamicClientRegistrationConfig{
+			Enabled:            true,
+			PersistCredentials: true,
+			StorageBackend:     "unknown",
+		}
+
+		_, err := NewDCRCredentialsStore(config, nil, logger)
+		if err == nil {
+			t.Error("Expected error for unknown backend")
+		}
+	})
+
+	t.Run("empty backend defaults to auto", func(t *testing.T) {
+		config := &DynamicClientRegistrationConfig{
+			Enabled:            true,
+			PersistCredentials: true,
+			StorageBackend:     "",
+		}
+
+		store, err := NewDCRCredentialsStore(config, nil, logger)
+		if err != nil {
+			t.Fatalf("Failed to create store with empty backend: %v", err)
+		}
+
+		// Should default to file (auto without redis)
+		_, ok := store.(*FileCredentialsStore)
+		if !ok {
+			t.Error("Expected FileCredentialsStore for empty backend")
+		}
+	})
+}
+
+// TestDynamicClientRegistrar_WithStore tests registrar with store
+func TestDynamicClientRegistrar_WithStore(t *testing.T) {
+	t.Parallel()
+
+	tempDir := t.TempDir()
+	basePath := filepath.Join(tempDir, "credentials.json")
+	logger := GetSingletonNoOpLogger()
+	store := NewFileCredentialsStore(basePath, logger)
+
+	config := &DynamicClientRegistrationConfig{
+		Enabled:            true,
+		PersistCredentials: true,
+	}
+
+	registrar := NewDynamicClientRegistrarWithStore(
+		nil, // httpClient
+		logger,
+		config,
+		"https://auth.example.com",
+		store,
+	)
+
+	if registrar == nil {
+		t.Fatal("Expected registrar but got nil")
+	}
+
+	if registrar.store == nil {
+		t.Error("Expected store to be set")
+	}
+
+	// Test SetStore
+	newStore := NewFileCredentialsStore(filepath.Join(tempDir, "new.json"), logger)
+	registrar.SetStore(newStore)
+
+	if registrar.store != newStore {
+		t.Error("SetStore did not update the store")
+	}
+}
+
+// TestDynamicClientRegistrar_CredentialsFromStore tests loading from store
+func TestDynamicClientRegistrar_CredentialsFromStore(t *testing.T) {
+	t.Parallel()
+
+	tempDir := t.TempDir()
+	basePath := filepath.Join(tempDir, "credentials.json")
+	logger := GetSingletonNoOpLogger()
+	store := NewFileCredentialsStore(basePath, logger)
+
+	providerURL := "https://auth.example.com"
+	ctx := context.Background()
+
+	// Pre-save credentials
+	testCreds := &ClientRegistrationResponse{
+		ClientID:              "pre-saved-client",
+		ClientSecret:          "pre-saved-secret",
+		ClientSecretExpiresAt: time.Now().Add(24 * time.Hour).Unix(),
+	}
+	if err := store.Save(ctx, providerURL, testCreds); err != nil {
+		t.Fatalf("Failed to pre-save credentials: %v", err)
+	}
+
+	config := &DynamicClientRegistrationConfig{
+		Enabled:            true,
+		PersistCredentials: true,
+	}
+
+	registrar := NewDynamicClientRegistrarWithStore(
+		nil,
+		logger,
+		config,
+		providerURL,
+		store,
+	)
+
+	// Test loading via the internal method
+	loaded, err := registrar.loadCredentialsFromStore(ctx)
+	if err != nil {
+		t.Fatalf("Failed to load from store: %v", err)
+	}
+	if loaded == nil {
+		t.Fatal("Expected credentials but got nil")
+	}
+	if loaded.ClientID != "pre-saved-client" {
+		t.Errorf("ClientID mismatch: got %s", loaded.ClientID)
+	}
+}
+
+// TestFileCredentialsStore_CorruptedFile tests handling of corrupted files
+func TestFileCredentialsStore_CorruptedFile(t *testing.T) {
+	t.Parallel()
+
+	tempDir := t.TempDir()
+	basePath := filepath.Join(tempDir, "credentials.json")
+	logger := GetSingletonNoOpLogger()
+	store := NewFileCredentialsStore(basePath, logger)
+
+	ctx := context.Background()
+	providerURL := "https://auth.example.com"
+
+	// Write corrupted JSON
+	filePath := store.getFilePath(providerURL)
+	if err := os.WriteFile(filePath, []byte("{corrupted json"), 0600); err != nil {
+		t.Fatalf("Failed to write corrupted file: %v", err)
+	}
+
+	// Should return error for corrupted file
+	_, err := store.Load(ctx, providerURL)
+	if err == nil {
+		t.Error("Expected error for corrupted JSON")
+	}
+}
+
+// TestFileCredentialsStore_DirectoryCreation tests auto directory creation
+func TestFileCredentialsStore_DirectoryCreation(t *testing.T) {
+	t.Parallel()
+
+	tempDir := t.TempDir()
+	deepPath := filepath.Join(tempDir, "deep", "nested", "path", "credentials.json")
+	logger := GetSingletonNoOpLogger()
+	store := NewFileCredentialsStore(deepPath, logger)
+
+	ctx := context.Background()
+	creds := &ClientRegistrationResponse{ClientID: "test"}
+
+	err := store.Save(ctx, "https://example.com", creds)
+	if err != nil {
+		t.Fatalf("Failed to save with nested directory: %v", err)
+	}
+
+	loaded, err := store.Load(ctx, "https://example.com")
+	if err != nil {
+		t.Fatalf("Failed to load after nested directory creation: %v", err)
+	}
+	if loaded == nil || loaded.ClientID != "test" {
+		t.Error("Failed to load credentials from nested directory")
+	}
+}

docs/CONFIGURATION.md

@@ -384,10 +384,14 @@ scopes:
 
 ### Dynamic Client Registration (RFC 7591)
 
+Dynamic Client Registration allows the middleware to automatically register itself with the OIDC provider, eliminating the need to manually create client credentials.
+
+**Basic Configuration (Single Instance):**
+
 ```yaml
 dynamicClientRegistration:
   enabled: true
-  initialAccessToken: "your-token"  # Optional
+  initialAccessToken: "your-token"  # Optional, if provider requires it
   persistCredentials: true
   credentialsFile: "/tmp/oidc-credentials.json"
   clientMetadata:
@@ -400,6 +404,35 @@ dynamicClientRegistration:
       - "refresh_token"
 ```
 
+**Multi-Replica Deployment (Kubernetes):**
+
+For Kubernetes deployments with multiple replicas, use Redis storage to share credentials across all instances and prevent registration race conditions:
+
+```yaml
+dynamicClientRegistration:
+  enabled: true
+  persistCredentials: true
+  storageBackend: "redis"  # Share credentials via Redis
+  redisKeyPrefix: "myapp:dcr:"  # Optional custom prefix
+  clientMetadata:
+    redirect_uris:
+      - "https://your-app.com/oauth2/callback"
+    client_name: "My Application"
+
+redis:
+  enabled: true
+  address: "redis:6379"
+  cacheMode: "redis"
+```
+
+**Storage Backend Options:**
+
+| Backend | Description | Use Case |
+|---------|-------------|----------|
+| `file` | Store credentials in local file | Single instance deployments |
+| `redis` | Store credentials in Redis | Multi-replica Kubernetes deployments |
+| `auto` | Use Redis if available, fallback to file | Flexible deployments (default) |
+
 ### Multi-Replica Deployment
 
 Without Redis, disable replay detection:

docs/index.html

@@ -193,7 +193,7 @@
                             </div>
                             <div>
                                 <h3 class="font-semibold text-gray-900 dark:text-gray-100 mb-1">Dynamic Registration</h3>
-                                <p class="text-sm text-gray-600 dark:text-gray-400">RFC 7591 Dynamic Client Registration for automatic client setup without manual configuration</p>
+                                <p class="text-sm text-gray-600 dark:text-gray-400">RFC 7591 Dynamic Client Registration with Redis storage support for multi-replica deployments</p>
                             </div>
                         </div>
                     </div>
@@ -862,6 +862,48 @@ spec:
                             </table>
                         </div>
                     </div>
+                    <div class="glass p-6 rounded-xl">
+                        <h3 class="font-semibold text-gray-900 dark:text-gray-100 mb-4">Dynamic Client Registration (RFC 7591)</h3>
+                        <p class="text-gray-600 dark:text-gray-400 mb-3 text-sm">Automatically register your application with the OIDC provider. Supports Redis storage for multi-replica deployments:</p>
+                        <div class="overflow-x-auto mb-4">
+                            <table class="w-full text-sm">
+                                <thead>
+                                    <tr class="border-b border-gray-200 dark:border-gray-700">
+                                        <th class="text-left py-2 px-3 text-gray-900 dark:text-gray-100">Parameter</th>
+                                        <th class="text-left py-2 px-3 text-gray-900 dark:text-gray-100">Default</th>
+                                        <th class="text-left py-2 px-3 text-gray-900 dark:text-gray-100">Description</th>
+                                    </tr>
+                                </thead>
+                                <tbody class="text-gray-600 dark:text-gray-400">
+                                    <tr class="border-b border-gray-100 dark:border-gray-800">
+                                        <td class="py-2 px-3"><code class="bg-gray-200 dark:bg-gray-700 px-1 rounded">dynamicClientRegistration.enabled</code></td>
+                                        <td class="py-2 px-3">false</td>
+                                        <td class="py-2 px-3">Enable dynamic client registration</td>
+                                    </tr>
+                                    <tr class="border-b border-gray-100 dark:border-gray-800">
+                                        <td class="py-2 px-3"><code class="bg-gray-200 dark:bg-gray-700 px-1 rounded">dynamicClientRegistration.persistCredentials</code></td>
+                                        <td class="py-2 px-3">true</td>
+                                        <td class="py-2 px-3">Persist registered credentials across restarts</td>
+                                    </tr>
+                                    <tr class="border-b border-gray-100 dark:border-gray-800">
+                                        <td class="py-2 px-3"><code class="bg-gray-200 dark:bg-gray-700 px-1 rounded">dynamicClientRegistration.storageBackend</code></td>
+                                        <td class="py-2 px-3">auto</td>
+                                        <td class="py-2 px-3">Storage backend: <code class="bg-gray-200 dark:bg-gray-700 px-1 rounded">file</code>, <code class="bg-gray-200 dark:bg-gray-700 px-1 rounded">redis</code>, or <code class="bg-gray-200 dark:bg-gray-700 px-1 rounded">auto</code> (uses Redis if available)</td>
+                                    </tr>
+                                    <tr class="border-b border-gray-100 dark:border-gray-800">
+                                        <td class="py-2 px-3"><code class="bg-gray-200 dark:bg-gray-700 px-1 rounded">dynamicClientRegistration.redisKeyPrefix</code></td>
+                                        <td class="py-2 px-3">dcr:creds:</td>
+                                        <td class="py-2 px-3">Redis key prefix for DCR credentials</td>
+                                    </tr>
+                                    <tr>
+                                        <td class="py-2 px-3"><code class="bg-gray-200 dark:bg-gray-700 px-1 rounded">dynamicClientRegistration.clientMetadata.redirect_uris</code></td>
+                                        <td class="py-2 px-3">-</td>
+                                        <td class="py-2 px-3">Redirect URIs for the registered client (required)</td>
+                                    </tr>
+                                </tbody>
+                            </table>
+                        </div>
+                    </div>
                     <div class="glass p-6 rounded-xl">
                         <h3 class="font-semibold text-gray-900 dark:text-gray-100 mb-3">Example: Security Headers with CORS</h3>
 

dynamic_client_registration.go

@@ -50,6 +50,7 @@ type DynamicClientRegistrar struct {
 	logger               *Logger
 	config               *DynamicClientRegistrationConfig
 	registrationResponse *ClientRegistrationResponse
+	store                DCRCredentialsStore // Storage backend for credentials
 	providerURL          string
 	mu                   sync.RWMutex
 }
@@ -73,8 +74,37 @@ func NewDynamicClientRegistrar(
 	}
 }
 
+// NewDynamicClientRegistrarWithStore creates a new dynamic client registrar with a specific storage backend
+func NewDynamicClientRegistrarWithStore(
+	httpClient *http.Client,
+	logger *Logger,
+	dcrConfig *DynamicClientRegistrationConfig,
+	providerURL string,
+	store DCRCredentialsStore,
+) *DynamicClientRegistrar {
+	if logger == nil {
+		logger = GetSingletonNoOpLogger()
+	}
+
+	return &DynamicClientRegistrar{
+		httpClient:  httpClient,
+		logger:      logger,
+		config:      dcrConfig,
+		providerURL: providerURL,
+		store:       store,
+	}
+}
+
+// SetStore sets the credentials store for the registrar
+// This allows setting the store after creation when the cache manager is available
+func (r *DynamicClientRegistrar) SetStore(store DCRCredentialsStore) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.store = store
+}
+
 // RegisterClient performs dynamic client registration with the OIDC provider
-// It first attempts to load existing credentials from a file if persistence is enabled,
+// It first attempts to load existing credentials from storage if persistence is enabled,
 // then registers a new client if no valid credentials exist.
 func (r *DynamicClientRegistrar) RegisterClient(ctx context.Context, registrationEndpoint string) (*ClientRegistrationResponse, error) {
 	if r.config == nil || !r.config.Enabled {
@@ -83,10 +113,13 @@ func (r *DynamicClientRegistrar) RegisterClient(ctx context.Context, registratio
 
 	// Try to load existing credentials if persistence is enabled
 	if r.config.PersistCredentials {
-		if resp, err := r.loadCredentials(); err == nil && resp != nil {
+		resp, err := r.loadCredentialsFromStore(ctx)
+		if err != nil {
+			r.logger.Debugf("Failed to load credentials from store: %v", err)
+		} else if resp != nil {
 			// Check if credentials are still valid (not expired)
 			if r.areCredentialsValid(resp) {
-				r.logger.Info("Loaded existing client credentials from file")
+				r.logger.Info("Loaded existing client credentials from storage")
 				r.mu.Lock()
 				r.registrationResponse = resp
 				r.mu.Unlock()
@@ -179,7 +212,7 @@ func (r *DynamicClientRegistrar) RegisterClient(ctx context.Context, registratio
 
 	// Persist credentials if enabled
 	if r.config.PersistCredentials {
-		if err := r.saveCredentials(&regResp); err != nil {
+		if err := r.saveCredentialsToStore(ctx, &regResp); err != nil {
 			r.logger.Errorf("Failed to persist client credentials: %v", err)
 			// Don't fail registration if persistence fails
 		}
@@ -315,7 +348,44 @@ func (r *DynamicClientRegistrar) credentialsFilePath() string {
 	return "/tmp/oidc-client-credentials.json"
 }
 
-// saveCredentials persists client credentials to a file
+// loadCredentialsFromStore loads client credentials from the configured storage backend
+// Falls back to legacy file-based loading if no store is configured
+func (r *DynamicClientRegistrar) loadCredentialsFromStore(ctx context.Context) (*ClientRegistrationResponse, error) {
+	// Use store if available
+	if r.store != nil {
+		return r.store.Load(ctx, r.providerURL)
+	}
+	// Fallback to legacy file-based loading
+	return r.loadCredentials()
+}
+
+// saveCredentialsToStore persists client credentials to the configured storage backend
+// Falls back to legacy file-based saving if no store is configured
+func (r *DynamicClientRegistrar) saveCredentialsToStore(ctx context.Context, resp *ClientRegistrationResponse) error {
+	// Use store if available
+	if r.store != nil {
+		return r.store.Save(ctx, r.providerURL, resp)
+	}
+	// Fallback to legacy file-based saving
+	return r.saveCredentials(resp)
+}
+
+// deleteCredentialsFromStore removes credentials from the configured storage backend
+// Falls back to legacy file-based deletion if no store is configured
+func (r *DynamicClientRegistrar) deleteCredentialsFromStore(ctx context.Context) error {
+	// Use store if available
+	if r.store != nil {
+		return r.store.Delete(ctx, r.providerURL)
+	}
+	// Fallback to legacy file-based deletion
+	filePath := r.credentialsFilePath()
+	if err := os.Remove(filePath); err != nil && !os.IsNotExist(err) {
+		return err
+	}
+	return nil
+}
+
+// saveCredentials persists client credentials to a file (legacy method)
 func (r *DynamicClientRegistrar) saveCredentials(resp *ClientRegistrationResponse) error {
 	filePath := r.credentialsFilePath()
 
@@ -333,7 +403,7 @@ func (r *DynamicClientRegistrar) saveCredentials(resp *ClientRegistrationRespons
 	return nil
 }
 
-// loadCredentials loads client credentials from a file
+// loadCredentials loads client credentials from a file (legacy method)
 func (r *DynamicClientRegistrar) loadCredentials() (*ClientRegistrationResponse, error) {
 	filePath := r.credentialsFilePath()
 
@@ -420,7 +490,7 @@ func (r *DynamicClientRegistrar) UpdateClientRegistration(ctx context.Context) (
 
 	// Persist updated credentials if enabled
 	if r.config.PersistCredentials {
-		if err := r.saveCredentials(&regResp); err != nil {
+		if err := r.saveCredentialsToStore(ctx, &regResp); err != nil {
 			r.logger.Errorf("Failed to persist updated credentials: %v", err)
 		}
 	}
@@ -527,11 +597,10 @@ func (r *DynamicClientRegistrar) DeleteClientRegistration(ctx context.Context) e
 	r.registrationResponse = nil
 	r.mu.Unlock()
 
-	// Remove credentials file if persistence is enabled
+	// Remove credentials from storage if persistence is enabled
 	if r.config.PersistCredentials {
-		filePath := r.credentialsFilePath()
+		if err := r.deleteCredentialsFromStore(ctx); err != nil {
-		if err := os.Remove(filePath); err != nil && !os.IsNotExist(err) {
+			r.logger.Errorf("Failed to remove credentials from storage: %v", err)
-			r.logger.Errorf("Failed to remove credentials file: %v", err)
 		}
 	}
 

internal/dcrstorage/file.go

@@ -0,0 +1,155 @@
+package dcrstorage
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+)
+
+// FileStore implements Store using file-based storage.
+// This is the default storage backend for backward compatibility with existing deployments.
+// For distributed environments, consider using RedisStore instead.
+type FileStore struct {
+	basePath string
+	logger   Logger
+	mu       sync.RWMutex
+}
+
+// NewFileStore creates a new file-based credentials store.
+// If basePath is empty, defaults to /tmp/oidc-client-credentials.json
+func NewFileStore(basePath string, logger Logger) *FileStore {
+	if basePath == "" {
+		basePath = "/tmp/oidc-client-credentials.json"
+	}
+	if logger == nil {
+		logger = NoOpLogger()
+	}
+	return &FileStore{
+		basePath: basePath,
+		logger:   logger,
+	}
+}
+
+// BasePath returns the base path used for storing credentials
+func (s *FileStore) BasePath() string {
+	return s.basePath
+}
+
+// GetFilePath returns the file path for storing credentials for a specific provider.
+// For multi-tenant scenarios, each provider gets a separate file based on URL hash.
+func (s *FileStore) GetFilePath(providerURL string) string {
+	if providerURL == "" {
+		return s.basePath
+	}
+
+	// Hash provider URL for filename safety and uniqueness
+	hash := sha256.Sum256([]byte(providerURL))
+	hashStr := hex.EncodeToString(hash[:8]) // Use first 8 bytes for shorter filename
+
+	ext := filepath.Ext(s.basePath)
+	base := strings.TrimSuffix(s.basePath, ext)
+	if ext == "" {
+		ext = ".json"
+	}
+
+	return fmt.Sprintf("%s-%s%s", base, hashStr, ext)
+}
+
+// Save stores the client registration response to a file
+func (s *FileStore) Save(ctx context.Context, providerURL string, creds *ClientRegistrationResponse) error {
+	if creds == nil {
+		return fmt.Errorf("credentials cannot be nil")
+	}
+
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	filePath := s.GetFilePath(providerURL)
+
+	// Ensure parent directory exists
+	dir := filepath.Dir(filePath)
+	if err := os.MkdirAll(dir, 0700); err != nil {
+		return fmt.Errorf("failed to create credentials directory: %w", err)
+	}
+
+	data, err := json.MarshalIndent(creds, "", "  ")
+	if err != nil {
+		return fmt.Errorf("failed to marshal credentials: %w", err)
+	}
+
+	// Write with restrictive permissions (owner read/write only)
+	if err := os.WriteFile(filePath, data, 0600); err != nil {
+		return fmt.Errorf("failed to write credentials file: %w", err)
+	}
+
+	s.logger.Debugf("Saved client credentials to %s", filePath)
+	return nil
+}
+
+// Load retrieves stored credentials from a file.
+// Returns nil, nil if no credentials file exists (not an error).
+func (s *FileStore) Load(ctx context.Context, providerURL string) (*ClientRegistrationResponse, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	filePath := s.GetFilePath(providerURL)
+
+	// #nosec G304 -- path is constructed from trusted config values via GetFilePath()
+	data, err := os.ReadFile(filePath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, nil // No credentials file exists - not an error
+		}
+		return nil, fmt.Errorf("failed to read credentials file: %w", err)
+	}
+
+	var creds ClientRegistrationResponse
+	if err := json.Unmarshal(data, &creds); err != nil {
+		return nil, fmt.Errorf("failed to parse credentials file: %w", err)
+	}
+
+	s.logger.Debugf("Loaded client credentials from %s", filePath)
+	return &creds, nil
+}
+
+// Delete removes the credentials file for a provider
+func (s *FileStore) Delete(ctx context.Context, providerURL string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	filePath := s.GetFilePath(providerURL)
+
+	if err := os.Remove(filePath); err != nil {
+		if os.IsNotExist(err) {
+			return nil // File doesn't exist, nothing to delete
+		}
+		return fmt.Errorf("failed to remove credentials file: %w", err)
+	}
+
+	s.logger.Debugf("Deleted client credentials from %s", filePath)
+	return nil
+}
+
+// Exists checks if credentials exist for a provider
+func (s *FileStore) Exists(ctx context.Context, providerURL string) (bool, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	filePath := s.GetFilePath(providerURL)
+
+	_, err := os.Stat(filePath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return false, nil
+		}
+		return false, fmt.Errorf("failed to check credentials file: %w", err)
+	}
+
+	return true, nil
+}

internal/dcrstorage/redis.go

@@ -0,0 +1,161 @@
+package dcrstorage
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"sync"
+	"time"
+)
+
+// Cache defines the interface for cache operations needed by RedisStore.
+// This allows the main package to provide a cache implementation without
+// creating circular dependencies.
+type Cache interface {
+	// Get retrieves a value from the cache
+	Get(key string) (any, bool)
+	// Set stores a value in the cache with a TTL
+	Set(key string, value any, ttl time.Duration) error
+	// Delete removes a value from the cache
+	Delete(key string)
+}
+
+// RedisStore implements Store using a Cache-backed storage.
+// This storage backend enables sharing DCR credentials across multiple Traefik instances
+// in distributed environments (e.g., Kubernetes with multiple ingress pods).
+type RedisStore struct {
+	cache     Cache
+	keyPrefix string
+	logger    Logger
+	mu        sync.RWMutex
+}
+
+// NewRedisStore creates a new cache-backed credentials store.
+// The cache should be configured with a Redis backend for distributed storage.
+// If keyPrefix is empty, defaults to "dcr:creds:"
+func NewRedisStore(cache Cache, keyPrefix string, logger Logger) *RedisStore {
+	if keyPrefix == "" {
+		keyPrefix = "dcr:creds:"
+	}
+	if logger == nil {
+		logger = NoOpLogger()
+	}
+	return &RedisStore{
+		cache:     cache,
+		keyPrefix: keyPrefix,
+		logger:    logger,
+	}
+}
+
+// makeKey creates a unique cache key for a provider URL.
+// Uses SHA256 hash of the provider URL for consistent key generation across nodes.
+func (s *RedisStore) makeKey(providerURL string) string {
+	if providerURL == "" {
+		return s.keyPrefix + "default"
+	}
+	hash := sha256.Sum256([]byte(providerURL))
+	return s.keyPrefix + hex.EncodeToString(hash[:])
+}
+
+// Save stores the client registration response in the cache.
+// TTL is calculated based on client_secret_expires_at if available.
+func (s *RedisStore) Save(ctx context.Context, providerURL string, creds *ClientRegistrationResponse) error {
+	if creds == nil {
+		return fmt.Errorf("credentials cannot be nil")
+	}
+
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	key := s.makeKey(providerURL)
+
+	// Calculate TTL based on client_secret_expires_at if available
+	ttl := 30 * 24 * time.Hour // Default: 30 days
+	if creds.ClientSecretExpiresAt > 0 {
+		expiresAt := time.Unix(creds.ClientSecretExpiresAt, 0)
+		ttl = time.Until(expiresAt)
+		if ttl < 0 {
+			return fmt.Errorf("credentials already expired")
+		}
+		// Add a small buffer to ensure we don't serve expired credentials
+		if ttl > time.Minute {
+			ttl -= time.Minute
+		}
+	}
+
+	// Serialize credentials to JSON for storage
+	data, err := json.Marshal(creds)
+	if err != nil {
+		return fmt.Errorf("failed to marshal credentials: %w", err)
+	}
+
+	// Store as string in cache (will be serialized by the cache backend)
+	if err := s.cache.Set(key, string(data), ttl); err != nil {
+		return fmt.Errorf("failed to store credentials in cache: %w", err)
+	}
+
+	s.logger.Debugf("Saved client credentials to cache with key %s (TTL: %v)", key, ttl)
+	return nil
+}
+
+// Load retrieves stored credentials from the cache.
+// Returns nil, nil if no credentials exist (not an error).
+func (s *RedisStore) Load(ctx context.Context, providerURL string) (*ClientRegistrationResponse, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	key := s.makeKey(providerURL)
+
+	value, exists := s.cache.Get(key)
+	if !exists {
+		return nil, nil // No credentials stored - not an error
+	}
+
+	// Handle different value types from cache
+	var jsonData string
+	switch v := value.(type) {
+	case string:
+		jsonData = v
+	case []byte:
+		jsonData = string(v)
+	default:
+		// Try to see if it's already the struct (from local cache)
+		if creds, ok := value.(*ClientRegistrationResponse); ok {
+			return creds, nil
+		}
+		return nil, fmt.Errorf("unexpected credentials type in cache: %T", value)
+	}
+
+	var creds ClientRegistrationResponse
+	if err := json.Unmarshal([]byte(jsonData), &creds); err != nil {
+		return nil, fmt.Errorf("failed to parse credentials from cache: %w", err)
+	}
+
+	s.logger.Debugf("Loaded client credentials from cache with key %s", key)
+	return &creds, nil
+}
+
+// Delete removes stored credentials from the cache
+func (s *RedisStore) Delete(ctx context.Context, providerURL string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	key := s.makeKey(providerURL)
+	s.cache.Delete(key)
+
+	s.logger.Debugf("Deleted client credentials from cache with key %s", key)
+	return nil
+}
+
+// Exists checks if credentials exist in the cache for a provider
+func (s *RedisStore) Exists(ctx context.Context, providerURL string) (bool, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	key := s.makeKey(providerURL)
+	_, exists := s.cache.Get(key)
+
+	return exists, nil
+}

internal/dcrstorage/storage.go

@@ -0,0 +1,90 @@
+// Package dcrstorage provides storage backends for OIDC Dynamic Client Registration credentials.
+// It supports both file-based and Redis-based storage for persisting client credentials
+// across application restarts and distributed deployments.
+package dcrstorage
+
+import (
+	"context"
+)
+
+// StorageBackend represents the type of storage backend for DCR credentials
+type StorageBackend string
+
+const (
+	// StorageBackendFile uses file-based storage (default for backward compatibility)
+	StorageBackendFile StorageBackend = "file"
+
+	// StorageBackendRedis uses Redis for distributed storage
+	StorageBackendRedis StorageBackend = "redis"
+
+	// StorageBackendAuto automatically selects Redis if available, otherwise file
+	StorageBackendAuto StorageBackend = "auto"
+)
+
+// Logger interface for DCR storage operations
+type Logger interface {
+	Debug(msg string)
+	Debugf(format string, args ...any)
+	Info(msg string)
+	Infof(format string, args ...any)
+	Error(msg string)
+	Errorf(format string, args ...any)
+}
+
+// ClientRegistrationResponse represents the response from a successful client registration (RFC 7591)
+type ClientRegistrationResponse struct {
+	SubjectType             string   `json:"subject_type,omitempty"`
+	LogoURI                 string   `json:"logo_uri,omitempty"`
+	RegistrationAccessToken string   `json:"registration_access_token,omitempty"`
+	RegistrationClientURI   string   `json:"registration_client_uri,omitempty"`
+	Scope                   string   `json:"scope,omitempty"`
+	TokenEndpointAuthMethod string   `json:"token_endpoint_auth_method,omitempty"`
+	TOSURI                  string   `json:"tos_uri,omitempty"`
+	PolicyURI               string   `json:"policy_uri,omitempty"`
+	ClientSecret            string   `json:"client_secret,omitempty"`
+	ApplicationType         string   `json:"application_type,omitempty"`
+	ClientID                string   `json:"client_id"`
+	ClientName              string   `json:"client_name,omitempty"`
+	JWKSURI                 string   `json:"jwks_uri,omitempty"`
+	ClientURI               string   `json:"client_uri,omitempty"`
+	Contacts                []string `json:"contacts,omitempty"`
+	GrantTypes              []string `json:"grant_types,omitempty"`
+	ResponseTypes           []string `json:"response_types,omitempty"`
+	RedirectURIs            []string `json:"redirect_uris,omitempty"`
+	ClientSecretExpiresAt   int64    `json:"client_secret_expires_at,omitempty"`
+	ClientIDIssuedAt        int64    `json:"client_id_issued_at,omitempty"`
+}
+
+// Store defines the interface for storing DCR credentials.
+// This abstraction allows different storage backends (file, Redis) to be used
+// for persisting OIDC Dynamic Client Registration credentials across nodes.
+type Store interface {
+	// Save stores the client registration response for a provider
+	// The providerURL is used as a key to support multi-tenant scenarios
+	Save(ctx context.Context, providerURL string, creds *ClientRegistrationResponse) error
+
+	// Load retrieves stored credentials for a provider
+	// Returns nil, nil if no credentials exist (not an error)
+	Load(ctx context.Context, providerURL string) (*ClientRegistrationResponse, error)
+
+	// Delete removes stored credentials for a provider
+	Delete(ctx context.Context, providerURL string) error
+
+	// Exists checks if credentials exist for a provider
+	Exists(ctx context.Context, providerURL string) (bool, error)
+}
+
+// noOpLogger is a no-op implementation of Logger for default use
+type noOpLogger struct{}
+
+func (n noOpLogger) Debug(msg string)                  {}
+func (n noOpLogger) Debugf(format string, args ...any) {}
+func (n noOpLogger) Info(msg string)                   {}
+func (n noOpLogger) Infof(format string, args ...any)  {}
+func (n noOpLogger) Error(msg string)                  {}
+func (n noOpLogger) Errorf(format string, args ...any) {}
+
+// NoOpLogger returns a no-op logger instance
+func NoOpLogger() Logger {
+	return noOpLogger{}
+}

internal/dcrstorage/storage_test.go

@@ -0,0 +1,464 @@
+package dcrstorage
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"sync"
+	"testing"
+	"time"
+)
+
+// mockCache implements Cache for testing
+type mockCache struct {
+	data map[string]cacheEntry
+	mu   sync.RWMutex
+}
+
+type cacheEntry struct {
+	value     any
+	expiresAt time.Time
+}
+
+func newMockCache() *mockCache {
+	return &mockCache{data: make(map[string]cacheEntry)}
+}
+
+func (m *mockCache) Get(key string) (any, bool) {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	entry, ok := m.data[key]
+	if !ok {
+		return nil, false
+	}
+	if time.Now().After(entry.expiresAt) {
+		return nil, false
+	}
+	return entry.value, true
+}
+
+func (m *mockCache) Set(key string, value any, ttl time.Duration) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.data[key] = cacheEntry{
+		value:     value,
+		expiresAt: time.Now().Add(ttl),
+	}
+	return nil
+}
+
+func (m *mockCache) Delete(key string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	delete(m.data, key)
+}
+
+func TestFileStore_SaveLoad(t *testing.T) {
+	t.Parallel()
+
+	tempDir := t.TempDir()
+	basePath := filepath.Join(tempDir, "credentials.json")
+
+	store := NewFileStore(basePath, nil)
+
+	testCreds := &ClientRegistrationResponse{
+		ClientID:                "test-client-id",
+		ClientSecret:            "test-client-secret",
+		ClientSecretExpiresAt:   time.Now().Add(24 * time.Hour).Unix(),
+		RegistrationAccessToken: "test-access-token",
+		RegistrationClientURI:   "https://example.com/register/test-client-id",
+		RedirectURIs:            []string{"https://app.example.com/callback"},
+		GrantTypes:              []string{"authorization_code", "refresh_token"},
+		ResponseTypes:           []string{"code"},
+		TokenEndpointAuthMethod: "client_secret_basic",
+	}
+
+	ctx := context.Background()
+	providerURL := "https://auth.example.com"
+
+	t.Run("save and load credentials", func(t *testing.T) {
+		err := store.Save(ctx, providerURL, testCreds)
+		if err != nil {
+			t.Fatalf("Failed to save credentials: %v", err)
+		}
+
+		loaded, err := store.Load(ctx, providerURL)
+		if err != nil {
+			t.Fatalf("Failed to load credentials: %v", err)
+		}
+
+		if loaded == nil {
+			t.Fatal("Expected credentials but got nil")
+		}
+
+		if loaded.ClientID != testCreds.ClientID {
+			t.Errorf("ClientID mismatch: got %s, want %s", loaded.ClientID, testCreds.ClientID)
+		}
+		if loaded.ClientSecret != testCreds.ClientSecret {
+			t.Errorf("ClientSecret mismatch: got %s, want %s", loaded.ClientSecret, testCreds.ClientSecret)
+		}
+		if loaded.RegistrationAccessToken != testCreds.RegistrationAccessToken {
+			t.Errorf("RegistrationAccessToken mismatch: got %s, want %s", loaded.RegistrationAccessToken, testCreds.RegistrationAccessToken)
+		}
+	})
+
+	t.Run("load non-existent credentials", func(t *testing.T) {
+		tempDir2 := t.TempDir()
+		store2 := NewFileStore(filepath.Join(tempDir2, "nonexistent.json"), nil)
+
+		loaded, err := store2.Load(ctx, "https://nonexistent.example.com")
+		if err != nil {
+			t.Fatalf("Unexpected error for non-existent file: %v", err)
+		}
+		if loaded != nil {
+			t.Error("Expected nil for non-existent credentials")
+		}
+	})
+
+	t.Run("exists check", func(t *testing.T) {
+		exists, err := store.Exists(ctx, providerURL)
+		if err != nil {
+			t.Fatalf("Exists check failed: %v", err)
+		}
+		if !exists {
+			t.Error("Expected credentials to exist")
+		}
+
+		exists, err = store.Exists(ctx, "https://nonexistent.example.com")
+		if err != nil {
+			t.Fatalf("Exists check failed: %v", err)
+		}
+		if exists {
+			t.Error("Expected credentials to not exist")
+		}
+	})
+
+	t.Run("delete credentials", func(t *testing.T) {
+		err := store.Delete(ctx, providerURL)
+		if err != nil {
+			t.Fatalf("Failed to delete credentials: %v", err)
+		}
+
+		exists, _ := store.Exists(ctx, providerURL)
+		if exists {
+			t.Error("Expected credentials to be deleted")
+		}
+	})
+
+	t.Run("delete non-existent credentials", func(t *testing.T) {
+		err := store.Delete(ctx, "https://nonexistent.example.com")
+		if err != nil {
+			t.Fatalf("Delete should not error for non-existent: %v", err)
+		}
+	})
+}
+
+func TestFileStore_MultiProvider(t *testing.T) {
+	t.Parallel()
+
+	tempDir := t.TempDir()
+	basePath := filepath.Join(tempDir, "credentials.json")
+	store := NewFileStore(basePath, nil)
+
+	ctx := context.Background()
+
+	provider1 := "https://auth1.example.com"
+	provider2 := "https://auth2.example.com"
+
+	creds1 := &ClientRegistrationResponse{
+		ClientID:     "client-1",
+		ClientSecret: "secret-1",
+	}
+	creds2 := &ClientRegistrationResponse{
+		ClientID:     "client-2",
+		ClientSecret: "secret-2",
+	}
+
+	if err := store.Save(ctx, provider1, creds1); err != nil {
+		t.Fatalf("Failed to save creds1: %v", err)
+	}
+	if err := store.Save(ctx, provider2, creds2); err != nil {
+		t.Fatalf("Failed to save creds2: %v", err)
+	}
+
+	loaded1, err := store.Load(ctx, provider1)
+	if err != nil {
+		t.Fatalf("Failed to load creds1: %v", err)
+	}
+	if loaded1.ClientID != "client-1" {
+		t.Errorf("Provider 1 ClientID mismatch: got %s", loaded1.ClientID)
+	}
+
+	loaded2, err := store.Load(ctx, provider2)
+	if err != nil {
+		t.Fatalf("Failed to load creds2: %v", err)
+	}
+	if loaded2.ClientID != "client-2" {
+		t.Errorf("Provider 2 ClientID mismatch: got %s", loaded2.ClientID)
+	}
+
+	if err := store.Delete(ctx, provider1); err != nil {
+		t.Fatalf("Failed to delete creds1: %v", err)
+	}
+
+	exists, _ := store.Exists(ctx, provider2)
+	if !exists {
+		t.Error("Provider 2 credentials should still exist")
+	}
+}
+
+func TestFileStore_ConcurrentAccess(t *testing.T) {
+	t.Parallel()
+
+	tempDir := t.TempDir()
+	basePath := filepath.Join(tempDir, "credentials.json")
+	store := NewFileStore(basePath, nil)
+
+	ctx := context.Background()
+	providerURL := "https://auth.example.com"
+
+	creds := &ClientRegistrationResponse{
+		ClientID:     "test-client",
+		ClientSecret: "test-secret",
+	}
+
+	var wg sync.WaitGroup
+	concurrency := 10
+
+	for range concurrency {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			_ = store.Save(ctx, providerURL, creds)
+		}()
+	}
+	wg.Wait()
+
+	for range concurrency {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			_, _ = store.Load(ctx, providerURL)
+		}()
+	}
+	wg.Wait()
+
+	loaded, err := store.Load(ctx, providerURL)
+	if err != nil {
+		t.Fatalf("Failed to load after concurrent access: %v", err)
+	}
+	if loaded == nil || loaded.ClientID != "test-client" {
+		t.Error("Credentials corrupted after concurrent access")
+	}
+}
+
+func TestFileStore_InvalidInput(t *testing.T) {
+	t.Parallel()
+
+	tempDir := t.TempDir()
+	basePath := filepath.Join(tempDir, "credentials.json")
+	store := NewFileStore(basePath, nil)
+
+	ctx := context.Background()
+
+	t.Run("save nil credentials", func(t *testing.T) {
+		err := store.Save(ctx, "https://example.com", nil)
+		if err == nil {
+			t.Error("Expected error for nil credentials")
+		}
+	})
+
+	t.Run("empty provider URL uses default path", func(t *testing.T) {
+		creds := &ClientRegistrationResponse{ClientID: "test"}
+		err := store.Save(ctx, "", creds)
+		if err != nil {
+			t.Fatalf("Save with empty provider URL failed: %v", err)
+		}
+
+		loaded, err := store.Load(ctx, "")
+		if err != nil {
+			t.Fatalf("Load with empty provider URL failed: %v", err)
+		}
+		if loaded == nil || loaded.ClientID != "test" {
+			t.Error("Failed to load credentials with empty provider URL")
+		}
+	})
+}
+
+func TestFileStore_DefaultPath(t *testing.T) {
+	t.Parallel()
+
+	store := NewFileStore("", nil)
+
+	if store.BasePath() == "" {
+		t.Error("Expected default base path")
+	}
+}
+
+func TestRedisStore_WithMockCache(t *testing.T) {
+	t.Parallel()
+
+	cache := newMockCache()
+	store := NewRedisStore(cache, "", nil)
+
+	ctx := context.Background()
+	providerURL := "https://auth.example.com"
+
+	testCreds := &ClientRegistrationResponse{
+		ClientID:                "redis-test-client",
+		ClientSecret:            "redis-test-secret",
+		ClientSecretExpiresAt:   time.Now().Add(24 * time.Hour).Unix(),
+		RegistrationAccessToken: "redis-test-token",
+		RedirectURIs:            []string{"https://app.example.com/callback"},
+	}
+
+	t.Run("save and load credentials", func(t *testing.T) {
+		err := store.Save(ctx, providerURL, testCreds)
+		if err != nil {
+			t.Fatalf("Failed to save credentials: %v", err)
+		}
+
+		loaded, err := store.Load(ctx, providerURL)
+		if err != nil {
+			t.Fatalf("Failed to load credentials: %v", err)
+		}
+
+		if loaded == nil {
+			t.Fatal("Expected credentials but got nil")
+		}
+		if loaded.ClientID != testCreds.ClientID {
+			t.Errorf("ClientID mismatch: got %s, want %s", loaded.ClientID, testCreds.ClientID)
+		}
+		if loaded.ClientSecret != testCreds.ClientSecret {
+			t.Errorf("ClientSecret mismatch: got %s, want %s", loaded.ClientSecret, testCreds.ClientSecret)
+		}
+	})
+
+	t.Run("exists check", func(t *testing.T) {
+		exists, err := store.Exists(ctx, providerURL)
+		if err != nil {
+			t.Fatalf("Exists check failed: %v", err)
+		}
+		if !exists {
+			t.Error("Expected credentials to exist")
+		}
+	})
+
+	t.Run("delete credentials", func(t *testing.T) {
+		err := store.Delete(ctx, providerURL)
+		if err != nil {
+			t.Fatalf("Failed to delete credentials: %v", err)
+		}
+
+		exists, _ := store.Exists(ctx, providerURL)
+		if exists {
+			t.Error("Expected credentials to be deleted")
+		}
+	})
+
+	t.Run("load non-existent credentials", func(t *testing.T) {
+		loaded, err := store.Load(ctx, "https://nonexistent.example.com")
+		if err != nil {
+			t.Fatalf("Unexpected error for non-existent: %v", err)
+		}
+		if loaded != nil {
+			t.Error("Expected nil for non-existent credentials")
+		}
+	})
+}
+
+func TestRedisStore_TTLFromExpiry(t *testing.T) {
+	t.Parallel()
+
+	cache := newMockCache()
+	store := NewRedisStore(cache, "", nil)
+
+	ctx := context.Background()
+
+	t.Run("expired credentials should fail", func(t *testing.T) {
+		expiredCreds := &ClientRegistrationResponse{
+			ClientID:              "expired-client",
+			ClientSecret:          "expired-secret",
+			ClientSecretExpiresAt: time.Now().Add(-1 * time.Hour).Unix(),
+		}
+
+		err := store.Save(ctx, "https://expired.example.com", expiredCreds)
+		if err == nil {
+			t.Error("Expected error for expired credentials")
+		}
+	})
+
+	t.Run("credentials without expiry use default TTL", func(t *testing.T) {
+		creds := &ClientRegistrationResponse{
+			ClientID:              "no-expiry-client",
+			ClientSecret:          "no-expiry-secret",
+			ClientSecretExpiresAt: 0,
+		}
+
+		err := store.Save(ctx, "https://noexpiry.example.com", creds)
+		if err != nil {
+			t.Fatalf("Failed to save credentials without expiry: %v", err)
+		}
+	})
+}
+
+func TestRedisStore_InvalidInput(t *testing.T) {
+	t.Parallel()
+
+	cache := newMockCache()
+	store := NewRedisStore(cache, "", nil)
+
+	ctx := context.Background()
+
+	t.Run("save nil credentials", func(t *testing.T) {
+		err := store.Save(ctx, "https://example.com", nil)
+		if err == nil {
+			t.Error("Expected error for nil credentials")
+		}
+	})
+}
+
+func TestFileStore_CorruptedFile(t *testing.T) {
+	t.Parallel()
+
+	tempDir := t.TempDir()
+	basePath := filepath.Join(tempDir, "credentials.json")
+	store := NewFileStore(basePath, nil)
+
+	ctx := context.Background()
+	providerURL := "https://auth.example.com"
+
+	filePath := store.GetFilePath(providerURL)
+	if err := os.WriteFile(filePath, []byte("{corrupted json"), 0600); err != nil {
+		t.Fatalf("Failed to write corrupted file: %v", err)
+	}
+
+	_, err := store.Load(ctx, providerURL)
+	if err == nil {
+		t.Error("Expected error for corrupted JSON")
+	}
+}
+
+func TestFileStore_DirectoryCreation(t *testing.T) {
+	t.Parallel()
+
+	tempDir := t.TempDir()
+	deepPath := filepath.Join(tempDir, "deep", "nested", "path", "credentials.json")
+	store := NewFileStore(deepPath, nil)
+
+	ctx := context.Background()
+	creds := &ClientRegistrationResponse{ClientID: "test"}
+
+	err := store.Save(ctx, "https://example.com", creds)
+	if err != nil {
+		t.Fatalf("Failed to save with nested directory: %v", err)
+	}
+
+	loaded, err := store.Load(ctx, "https://example.com")
+	if err != nil {
+		t.Fatalf("Failed to load after nested directory creation: %v", err)
+	}
+	if loaded == nil || loaded.ClientID != "test" {
+		t.Error("Failed to load credentials from nested directory")
+	}
+}

main.go

@@ -433,6 +433,19 @@ func (t *TraefikOidc) performDynamicClientRegistration() {
 			t.dcrConfig,
 			t.providerURL,
 		)
+
+		// Set up storage backend for credentials persistence
+		if t.dcrConfig.PersistCredentials {
+			cacheManager := GetGlobalCacheManagerWithConfig(t.goroutineWG, nil)
+			store, err := NewDCRCredentialsStore(t.dcrConfig, cacheManager, t.logger)
+			if err != nil {
+				t.logger.Errorf("Failed to create DCR credentials store: %v", err)
+				// Continue without persistence - registration will still work
+			} else {
+				t.dynamicClientRegistrar.SetStore(store)
+				t.logger.Debugf("DCR credentials store initialized with backend: %s", t.dcrConfig.StorageBackend)
+			}
+		}
 	}
 
 	// Get registration endpoint (from metadata or config override)

settings.go

@@ -98,6 +98,13 @@ type DynamicClientRegistrationConfig struct {
 	InitialAccessToken   string                      `json:"initialAccessToken,omitempty"`
 	RegistrationEndpoint string                      `json:"registrationEndpoint,omitempty"`
 	CredentialsFile      string                      `json:"credentialsFile,omitempty"`
+	// StorageBackend specifies where to store DCR credentials: "file", "redis", or "auto"
+	// - "file": Use file-based storage (default for backward compatibility)
+	// - "redis": Use Redis exclusively (fails if Redis unavailable)
+	// - "auto": Use Redis if available, fallback to file (default)
+	StorageBackend string `json:"storageBackend,omitempty"`
+	// RedisKeyPrefix is the prefix for Redis keys when using Redis storage (default: "dcr:creds:")
+	RedisKeyPrefix     string `json:"redisKeyPrefix,omitempty"`
 	Enabled            bool   `json:"enabled"`
 	PersistCredentials bool   `json:"persistCredentials"`
 }

universal_cache_singleton.go

@@ -21,6 +21,7 @@ type UniversalCacheManager struct {
 	introspectionCache  *UniversalCache
 	tokenCache          *UniversalCache
 	metadataCache       *UniversalCache
+	dcrCredentialsCache *UniversalCache // DCR credentials storage for distributed environments
 	logger              *Logger
 	blacklistCache      *UniversalCache
 	cancel              context.CancelFunc
@@ -349,6 +350,19 @@ func initializeCachesWithRedis(manager *UniversalCacheManager, logger *Logger, r
 		SkipAutoCleanup: true, // Managed cleanup
 	})
 
+	// DCR credentials cache - CRITICAL for distributed DCR across multiple nodes
+	// Uses Redis backend to share client credentials across all Traefik replicas
+	manager.dcrCredentialsCache = NewUniversalCacheWithBackend(
+		UniversalCacheConfig{
+			Type:            CacheTypeGeneral,
+			MaxSize:         100,                 // Few providers expected
+			DefaultTTL:      30 * 24 * time.Hour, // 30 days default (credentials are long-lived)
+			Logger:          logger,
+			SkipAutoCleanup: true, // Managed cleanup
+		},
+		createBackend("dcr"),
+	)
+
 	logger.Infof("Cache manager initialized with %s backend configuration", redisConfig.CacheMode)
 }
 
@@ -396,6 +410,7 @@ func (m *UniversalCacheManager) performConsolidatedCleanup() {
 		m.sessionCache,
 		m.introspectionCache,
 		m.tokenTypeCache,
+		m.dcrCredentialsCache,
 	}
 	m.mu.RUnlock()
 
@@ -458,6 +473,13 @@ func (m *UniversalCacheManager) GetTokenTypeCache() *UniversalCache {
 	return m.tokenTypeCache
 }
 
+// GetDCRCredentialsCache returns the DCR credentials cache for distributed storage
+func (m *UniversalCacheManager) GetDCRCredentialsCache() *UniversalCache {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.dcrCredentialsCache
+}
+
 // Close shuts down all caches and the consolidated cleanup routine
 func (m *UniversalCacheManager) Close() error {
 	// Stop the consolidated cleanup routine first
@@ -473,7 +495,7 @@ func (m *UniversalCacheManager) Close() error {
 
 	// Close all caches first (they won't close the shared backend)
 	for _, cache := range []*UniversalCache{
-		m.tokenCache, m.blacklistCache, m.metadataCache, m.jwkCache, m.sessionCache, m.introspectionCache, m.tokenTypeCache,
+		m.tokenCache, m.blacklistCache, m.metadataCache, m.jwkCache, m.sessionCache, m.introspectionCache, m.tokenTypeCache, m.dcrCredentialsCache,
 	} {
 		if cache != nil {
 			_ = cache.Close() // Safe to ignore: best effort cache cleanup