Rate Limiting and Quota Management Questions

Designing and implementing throttling and quota controls to protect services and enforce fair usage. Candidates should be familiar with common algorithms such as token bucket, leaky bucket, sliding window log, and sliding window counter, and understand the tradeoffs in accuracy, memory use, and latency. Evaluate single process implementations and distributed approaches including Redis based counters, sharded counters, central token services, and edge enforcement at gateways or content delivery layers. Be prepared to discuss per user and per endpoint quotas, burst handling, backpressure, client facing rate limit headers, monitoring and alerting, testing under contention, and how to handle failures and partial network partitions with fail open versus fail closed semantics and interaction with idempotency and retry strategies.