Design the asynchronous backbone that decouples services and manages traffic at internet scale
Design distributed rate limiting with token bucket, sliding window algorithms, Redis-based counters, and hierarchical limits (per-user, per-API, global).
Design a Kafka-like distributed queue with partitioned logs, consumer groups, exactly-once semantics, and millions of messages/second throughput.
Design a counting system for likes/views handling billions of increments with eventual consistency, sharded counters, and HyperLogLog.
Design distributed Cron with time-wheel algorithm, exactly-once execution, job dependencies, retry logic, and leader election.
Design reliable webhook delivery with exponential backoff, circuit breakers, HMAC signatures, dead letter queues, and at-least-once guarantees.