Most engineers don't fail system design rounds because they don't know caching or Kafka. They fail because they can't explain the trade-off clearly, can't say when not to use it, or freeze on the follow-up question.

The System Design Interview Crack Sheet fixes exactly that. It's a 64-page visual revision guide that turns 49 core concepts into answers you can say out loud.

📘 What you get

✅ 49 concepts, one page each. Definition, why it matters, use when / avoid when, benefit, cost and failure mode. Every page has the same layout, so you find things fast. ✅ 98 interviewer questions with ready "Say:" answers. Each answer is 25–45 words (about 30 seconds) and written to be spoken, not memorised. ✅ 49 colour-coded diagrams. Each one shows the real mechanism step by step, and no two are alike. ✅ 49 follow-up questions, the kind interviewers use to probe deeper, each discussed in the appendix with assumptions and alternatives. ✅ Decision matrix to pick the right database, cache, queue or delivery guarantee quickly. ✅ Acronym glossary covering CAP, PACELC, CDC, CQRS, SLO, RPO and more. ✅ Clickable revision map that takes you to any concept in one tap.

Start Here: interview approach, requirements & SLOs, capacity estimation, latency & queues

Request Path: scaling, DNS, load balancing, API gateway, CDN, monolith vs microservices

Data & Cache: cache-aside, eviction, stampedes & hot keys, SQL vs NoSQL, indexes, B-tree vs LSM, replication, sharding, consistent hashing, transactions & isolation

Distributed Correctness: CAP & PACELC, quorums, consensus & leader election, distributed locks & fencing, idempotency, clocks & ordering

Async Systems: queues & pub/sub, Kafka partitions & consumer groups, delivery guarantees, outbox & CDC, sagas, CQRS & event sourcing, stream processing

Reliability & Security: rate limiting, timeouts/retries/circuit breakers, backpressure, auth & secrets, observability, multi-region & DR, multi-tenancy, safe deployments

Specialized Building Blocks: WebSocket/SSE, large uploads, search & inverted indexes, Bloom filters, geo indexes, pagination

🎯 This is for you if… • You have a backend, SDE-2, senior or staff interview coming up • You've watched hours of videos but still struggle to explain concepts clearly • You want a last-week revision tool, not another 400-page book • You learn better from diagrams than from walls of text

💡 Why this and not a course or a big book? Courses and books teach. This sheet is built for revision and recall: one page per concept, one diagram, two answers to say out loud. Read it on a commute, review it the night before, and walk in with answers ready.

📦 Details • 64-page PDF · instant download • Works on laptop, tablet and phone • Free updates to this edition (currently v1.2.2) • Created by Kalpesh Prajapati, backend engineer

Honest note: this is a concept revision guide. It doesn't cover every possible interview question, and no interview outcome is guaranteed.