Learn system design, the way it's actually interviewed
Frameworks, full problem walkthroughs, and the concepts that come up again and again — written to make you better in the room, not just better-read.
Guides
Frameworks and prep plans to walk in ready.
System Design Interview Cheat Sheet
A fast reference for system design interviews: the 45-minute framework, latency and capacity numbers to memorize, building blocks and when to use them, and a per-phase checklist.
Read the post →Back-of-the-Envelope Estimation for System Design Interviews
How to estimate scale in a system design interview: the numbers to know, a repeatable method, and a worked example showing how the math drives your design.
Read the post →How to Prepare for a System Design Interview: A Complete 2026 Guide
A step-by-step plan to prepare for system design interviews — the framework, what interviewers score, a 4-week study schedule, and the mistakes that sink strong engineers.
Read the post →System Design Interview Questions: The Practice List
A curated list of common system design interview questions by difficulty — what each one tests, with links to full walkthroughs — so you can plan your practice.
Read the post →Problem Walkthroughs
Full, end-to-end solutions to the problems interviewers actually ask.
Design a URL Shortener — System Design Interview Walkthrough
A full walkthrough of the URL shortener system design question: requirements, API, key generation, storage sizing, caching, and the follow-ups interviewers always ask.
Read the post →Design Twitter's News Feed — System Design Interview Walkthrough
A full walkthrough of the Design Twitter question: the home timeline, fan-out on write vs. read, the celebrity problem and the hybrid answer, storage, and caching.
Read the post →Design a Chat System (WhatsApp/Messenger) — System Design Walkthrough
A full walkthrough of the chat system design question: WebSocket connections, message flow, delivery guarantees, idempotency, presence, groups, and offline delivery.
Read the post →Design a Rate Limiter — System Design Interview Walkthrough
A full walkthrough of the rate limiter design question: token bucket vs. sliding window, where the state lives, atomicity in Redis, and fail-open vs. fail-closed.
Read the post →Design YouTube (Video Streaming) — System Design Interview Walkthrough
A full walkthrough of the Design YouTube question: chunked uploads, the transcoding pipeline, adaptive bitrate streaming (HLS/DASH), CDN delivery, and view counting.
Read the post →Design Uber (Ride-Matching) — System Design Interview Walkthrough
A full walkthrough of the Design Uber question: geospatial indexing (geohash/S2/H3), high-throughput location updates, the matching flow, and driver reservation.
Read the post →Concepts
The building blocks that come up again and again.
Database Replication Explained: Leaders, Lag, and Failover
How replication really works: the ordered log followers replay, sync vs. async commit costs, the anomalies lag causes, and why failover is the dangerous part.
Read the post →Database Sharding Explained: Shard Keys, Resharding & the Limits
When the numbers justify sharding, how to choose a shard key, range vs. hash vs. directory mapping, logical shards for resharding, and what it never fixes.
Read the post →Message Queues Explained: Kafka vs. RabbitMQ vs. SQS
What a queue actually buys you, queue vs. log semantics, at-least-once delivery and idempotent consumers, partitions and ordering, and how to pick a broker.
Read the post →Consistent Hashing Explained (with Diagrams)
Why modulo hashing collapses when the cluster changes, how the hash ring fixes it, why virtual nodes are mandatory in production, and what the ring still can't solve.
Read the post →The CAP Theorem Explained (for System Design Interviews)
What the CAP theorem actually says, why 'pick two of three' misleads, what a client sees on each side of the choice, PACELC, and why it's per-operation.
Read the post →Caching Strategies Explained: Cache-Aside, Write-Through & More
Read and write caching patterns with the arithmetic: cache-aside, write-through/back/around, why to delete rather than update, sizing, and the four ways caches fail.
Read the post →SQL vs NoSQL: How to Choose in a System Design Interview
How to choose between SQL and NoSQL by access pattern: what actually differs, where the write ceiling really is, the four shapes of NoSQL, and what each costs you.
Read the post →Mobile
iOS and Android system design — a different round from backend.
iOS System Design Interviews: What's Different and How to Prepare
Mobile system design rounds aren't backend interviews. Learn what iOS interviewers actually probe — offline, memory, battery, process lifecycle — and how to prepare.
Read the post →Android System Design Interviews: What to Expect and How to Prepare
Android design rounds test the client, not the backend. Learn what interviewers probe — offline, memory, battery, process death — and the Android APIs to know.
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