Status: IN
Three systems implement idempotency by keying on opaque identifiers (idempotency key, event ID) without verifying that the associated payload matches the original request, silently returning cached results even when parameters differ.
hotel returns cached reservation ignoring guest/dates/room, payment maps key→payment ID without param check, ad-click dedup keys on event_id alone — all three trade payload-awareness for implementation simplicity
Depends on (SL): hotel-idempotency-ignores-params, payment-idempotency-is-key-based, ad-click-dedup-global-not-per-ad