System Design Interview Questions: the 2026 shortlist

System design interviews often use seemingly simple prompts like designing a URL shortener, a rate limiter, or WhatsApp to test scalability. While basic implementations are trivial, interviewers focus on how designs handle billions of requests, node failures, and distributed counters. Success depends on navigating complex follow-ups regarding consistency, persistent connections, and delivery guarantees. A structured five-step framework helps candidates address a shortlist of twenty-five repeating questions that determine whether they pass the technical round.