Event Sourcing

Event Sourcing ensures that all changes to application state are stored as a sequence of events. We don't just store the current state; we store "what happened".

When to Use

• Audit Logs: When you need to know exactly how you got to the current state (Banking, Legal).
• Temporal Queries: "What did the system look like last Tuesday?".
• Intent Capture: distinguishing between "Correction" vs "Update".

Quick Start (Conceptual)

Traditional (State Stored): Order { id: 1, status: 'Shipped' } -> Update to 'Delivered' -> Order { id: 1, status: 'Delivered' } (History lost)

Event Sourcing (Events Stored):