Backend System Design Patterns Questions

Common backend problem patterns and their implementations in production systems. Typical topics include designing caches and eviction policies such as least recently used, implementing rate limiters with token bucket or sliding window algorithms, building URL shortener services, pub sub and message bus designs, circuit breakers and bulkheads, backpressure, cache invalidation strategies, and patterns for ensuring idempotent processing and message ordering. Interviewers assess algorithmic correctness, performance characteristics, locking and concurrency implications, and operational considerations.