Pattern Library

A catalogue of design patterns used in the Granit framework, organized by category.

Each pattern documents the general concept, how it is implemented in Granit, and references to the actual source files where the pattern is applied.

Architecture patterns

Pattern	Description
Module System	Topological loading with [DependsOn]
Hexagonal Architecture	Ports and Adapters for infrastructure decoupling
Layered Architecture	Domain / Application / Infrastructure separation
Middleware Pipeline	Dual ASP.NET Core + Wolverine pipeline
Event-Driven	IDomainEvent (local) + IIntegrationEvent (durable)
REPR	Minimal API Request-Endpoint-Response
CQRS	IReader / IWriter separation, ArchUnitNET enforcement
Anti-Corruption Layer	Isolation of Keycloak, S3, Brevo, FCM via internal DTOs

Cloud and SaaS patterns

Pattern	Description
Multi-Tenancy	3 isolation strategies, soft dependency, async propagation
Feature Flags	Multi-level resolution Tenant to Plan to Default
Transactional Outbox	Atomic event publishing via Wolverine Outbox
Idempotency	Stripe-style HTTP idempotency with state machine
Pre-Signed URL	Direct-to-cloud S3 upload/download
Sidecar / Behavior	Context propagation via Wolverine Behaviors
Circuit Breaker and Retry	Standard resilience + Wolverine RetryWithCooldown
Cache-Aside	Double-check locking + HybridCache L1/L2
Rate Limiting	Per-tenant rate limiting with dynamic quotas
Saga / Process Manager	GDPR export, import/export orchestrators
Fan-Out	Wolverine cascade for notifications and webhooks
Claim Check	Soft dependency IClaimCheckStore for large payloads
Bulkhead Isolation	Queue isolation, parallelism, tenant quotas

GoF behavioral patterns

Pattern	Description
Strategy	TenantIsolationStrategy, IBlobKeyStrategy, IStringEncryptionProvider
Chain of Responsibility	TenantResolverPipeline, blob validation
Command	SendWebhookCommand, RunMigrationBatchCommand
Template Method	GranitModule lifecycle, GranitValidator
State Machine	IdempotencyState, BlobStatus
Observer / Event	Wolverine implicit event subscription
Mediator	Wolverine message bus
Null Object	NullTenantContext, NullCacheValueEncryptor

GoF creational patterns

Pattern	Description
Factory Method	VaultClientFactory, DbContext tenant factories
Singleton	AsyncLocal singletons, NullTenantContext.Instance
Builder	Fluent AddGranit*() extensions

GoF structural patterns

Pattern	Description
Adapter	TypedKeyCacheServiceAdapter, S3BlobClient
Decorator	DistributedCacheService, CachedLocalizationOverrideStore
Proxy	FilterProxy for EF Core, Interceptors
Facade	DefaultBlobStorage, GranitExceptionHandler
Composite	Auditable entity hierarchy

Data patterns

Pattern	Description
Repository	Store interfaces + EF Core / InMemory implementations
Soft Delete	ISoftDeletable + SoftDeleteInterceptor (GDPR)
Data Filtering	IDataFilter with ImmutableDictionary AsyncLocal
Unit of Work	Implicit DbContext + interceptor chain
Specification	QueryDefinition whitelist-first, expression trees

Concurrency patterns

Pattern	Description
Scope / Context Manager	using pattern for context restoration
Copy-on-Write	ImmutableDictionary for thread-safe state
Double-Check Locking	Anti-stampede on cache miss

.NET idiom patterns

Pattern	Description
Expression Trees	Dynamic EF Core query filter construction
Marker Interface	ISoftDeletable, IMultiTenant, IDomainEvent
Options Pattern	93 Options classes, ValidateOnStart

Security patterns

Pattern	Description
Claims-Based Identity	JWT Keycloak + dynamic RBAC
Guard Clause	Systematic fail-fast, semantic exceptions

Granit-specific variants

Pattern	Description
Granit Variants	10 hybrid patterns unique to Granit