System Design Interviews, Real

Reading the Prompt: What's Actually Being Asked

Before drawing a single box, learn how to decode interviewer intent, disambiguate scope, and pick up on the signals that separate a great start from a mediocre one.

Capacity Estimation That Holds Up

Back-of-envelope math is not a party trick — learn how to anchor estimates in real numbers, catch common errors, and use sanity checks that actually impress interviewers.

The Five-Box Drawing and What Each Box Hides

Every system design whiteboard looks the same — client, load balancer, app servers, cache, database — but each box conceals decisions that separate junior candidates from senior ones.

Trade-off Vocabulary That Lands

CAP theorem and PACELC are often name-dropped and rarely understood — learn to use consistency and availability vocabulary precisely so your trade-off arguments actually move interviews forward.

Newsfeed Walkthrough

Designing a social newsfeed forces you to confront fanout strategy, ranking pipeline complexity, and storage tradeoffs that most candidates get wrong in the same predictable ways.

Ride-Sharing Walkthrough

Designing a ride-sharing platform requires geo-spatial indexing, low-latency driver matching, and real-time location updates — three distinct problems most candidates collapse into one.

Rate-Limiter Walkthrough

Token bucket, sliding window, and fixed window are not interchangeable — understand the precision-cost tradeoff of each algorithm and how distributed counters change the calculus entirely.

Distributed Search Walkthrough

Building a search system at scale requires sharding decisions, ranking pipelines, and replication strategies that are fundamentally different from the search libraries most engineers have actually used.

Chat Walkthrough

Chat systems hide four distinct hard problems — message fanout, total ordering, presence tracking, and push delivery — that most candidates conflate into a single WebSocket diagram.

The Follow-ups They Don't Tell You About

Failure scenarios, billing edge cases, and regulatory probes are the follow-up questions that expose the gap between candidates who have read about systems and those who have operated them.