idempotency Shipped
What this lens looks for
User actions and system operations safe to repeat without duplicate side effects; buttons debounced or disabled during async operations; idempotency keys on API calls with side effects; database migrations safe to run multiple times; state transitions check current state before applying
What its verifier checks
Submit buttons disabled or debounced during in-flight requests; idempotency keys present on write API calls; migration scripts use IF NOT EXISTS or equivalent guards; state transition logic reads current state before writing