How to Pass System Design Interviews at FAANG
System design interviews are among the most challenging and high-stakes rounds at FAANG companies. Unlike coding interviews where there is often one correct answer, system design questions are open-ended and test your ability to think through trade-offs, scale, and architecture.
The key to succeeding is having a repeatable framework. Start every question by clarifying requirements — functional and non-functional. Ask about expected scale (users, requests per second, data volume). This shows the interviewer you think before you build.
Next, sketch a high-level architecture. Identify the major components: load balancers, application servers, databases, caches, message queues. Draw the data flow from client to server and back. Keep it simple at first — you can add complexity later.
For storage, choose between SQL and NoSQL based on your access patterns. If you need strong consistency and complex queries, go with PostgreSQL or MySQL. If you need horizontal scalability and flexible schemas, consider DynamoDB, Cassandra, or MongoDB.
Caching is almost always part of the answer. Use Redis or Memcached to reduce database load. Discuss cache invalidation strategies — write-through, write-behind, or TTL-based expiration. Mention CDNs for static content.
Finally, discuss trade-offs. Every design decision has consequences. CAP theorem, consistency vs availability, synchronous vs asynchronous processing, monolith vs microservices. The interviewer wants to see that you understand these trade-offs, not that you pick the "right" answer.
Practice with real systems: design Twitter, design Uber, design a URL shortener. Use Interview AI Buddy to get real-time feedback on your approach during mock sessions.
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