Popular System Design Interviews Articles

A system design interview evaluates how an engineer turns an ambiguous product problem into a practical architecture. The goal is rarely to discover one perfect design. Interviewers are more interested in how requirements are clarified, assumptions are made, scale is estimated, components are select

A leaderboard looks simple at small scale: store each user's score, sort by score, and return the first 100 rows. At millions of users and thousands of score updates per second, that approach becomes expensive quickly.

An API rate limiter sounds simple: count requests and reject clients that exceed a limit. The design becomes much harder when requests are handled by dozens or hundreds of application instances across multiple servers, availability zones, or regions.

A payment request times out. The customer sees an error and presses Pay again. The first request may have failed, or it may have successfully charged the card while only the response was lost.

System design interviews are rarely failed because a candidate has never heard of caching, load balancing, replication, queues, or database sharding. More often, the problem is how those concepts are applied : designing before understanding requirements, estimating numbers that never influence the a