# Strangler-fig checklist for serverless modernization

## Week 0 — seams

- [ ] Map top 10 endpoints by RPS and change frequency
- [ ] Identify write boundaries (orders, payments, identity) vs read-only
- [ ] Choose first extract: high change, low blast radius
- [ ] Define rollback: feature flag or weighted Route 53 / API Gateway canary

## Extract 1

- [ ] New API Gateway route → Lambda (or LMI) for the capability
- [ ] Shared data access: anti-corruption layer; no dual-write without outbox
- [ ] Events: publish domain event on success to EventBridge
- [ ] Observability: traces across monolith + function (X-Ray / OTel)
- [ ] Load test at 2× current peak for that route

## Extract N

- [ ] Retire monolith code path behind flag
- [ ] Delete dead code within 30 days of 100% traffic
- [ ] Cost review: Lambda vs LMI vs Fargate for that shape
- [ ] Update runbooks and on-call

## Stop conditions

- Dual-write without idempotency keys
- Shared mutable DB tables without ownership
- Cross-service sync HTTP > 3 hops in the critical path