Backend API Design and Problem Solving Questions

Evaluate the candidate on designing and implementing backend services and solving algorithmic problems that arise in production systems. Topics include selection of appropriate data structures and algorithmic patterns for performance and memory, designing REST and GraphQL application programming interface endpoints with input validation pagination and versioning, handling business logic deterministically and idempotently, batching and pagination strategies, and trade offs around latency throughput and consistency. Candidates should also cover concurrency control and thread safety considerations request retry and backoff semantics caching placement and invalidation strategies and how they test and observe backend behavior in production.