Interview Q&A / System Design

1. What does at-least-once delivery mean, and can you get exactly-once?

   At-least-once means a message is never lost but may be delivered more than once. True exactly-once delivery is not practical across a network, so systems use at-least-once plus idempotent consumers to get exactly-once effects.

   IntermediateQuick answer1 min read
2. What is backpressure and how do you handle a queue that keeps growing?

   Backpressure means slowing or limiting producers when consumers cannot keep up. For a growing queue, add consumers, make processing faster, reject or throttle new work, and set limits so the queue cannot grow without bound.

   IntermediateQuick answer1 min read
3. Why should retries use exponential backoff with jitter?

   Backoff spaces out retries (1s, 2s, 4s...) so a struggling service gets room to recover. Jitter adds randomness so thousands of clients do not all retry at the same instant and cause a retry storm.

   IntermediateQuick answer1 min read