An API contract names the operation, identifies the resource and states what the caller receives. A read should not create an order as a side effect. A creation endpoint needs a defined response and failure behavior so the caller can recover when a response is lost. For retryable writes, an idempotency key identifies one intended operation across repeated requests. The server must store or enforce that identity with the operation's result.
Pagination needs a stable order. Offset pagination can skip or repeat rows when earlier rows are inserted or removed. A cursor using an ordering key and a unique tie-breaker can continue from a known boundary. The exercises check endpoint structure and reasoned behavior, not a vendor's syntax. Enter the fields the caller needs and explain what happens under a timeout, a duplicate write or equal timestamps.