Implement event sourcing and CQRS patterns using event stores, aggregates, and projections. Use when building audit trails, temporal queries, or systems requiring full history.

Event Sourcing Table of Contents [Overview]( overview) [When to Use]( when to use) [Quick Start]( quick start) [Reference Guides]( reference guides) [Best Practices]( best practices) Overview Store state changes as a sequence of events rather than the current state, enabling temporal queries, audit trails, and event replay. When to Use Audit trail requirements Temporal queries (state at any point in time) Event driven microservices CQRS implementations Financial systems Complex domain models Debugging and analysis Compliance and regulation Quick Start Minimal working example: Reference Guides Detailed implementations in the references/ directory: Guide Contents [Event Store (TypeScript)](references/event store typescript.md) Event Store (TypeScript) [Projections (Read Models)](references/projections read models.md) Projections (Read Models) [Event Store with PostgreSQL](references/event store with postgresql.md) Event Store with PostgreSQL [Snapshots for Performance](references/snapshots for performance.md) Snapshots for Performance Best Practices ✅ DO Store events immutably Version your events Use optimistic concurrency Create snapshots for performance Use projections for queries Keep events small and focused Include metadata (timestamp, user, etc.) Handle event versioning/migration ❌ DON'T Mutate past events Store current state only Skip concurrency checks Query event store for reads Make events too large Forget about event schema evolution

event-sourcing