Event sourcing

Intent

Persist state changes as an append-only sequence of events and reconstruct current state by replaying them.

Use when

• You need strong auditability/temporal correctness and the ability to rebuild projections.
• The domain benefits from explicit event histories (debugging, analytics, replay).

Avoid / watch-outs

• Event sourcing is not a free upgrade; it adds projection rebuild, schema evolution, and ops complexity.
• Plan event versioning and migration strategies early.

Skill mapping

• spec: event schemas, versioning, replay rules, and rebuild acceptance criteria.
• observability: replay/projection metrics and debuggability.
• testing: tests for event replay/projection correctness and backward compatibility.