System Design Interview Questions

System design interviews are not really testing whether you have memorised a reference architecture. They are testing whether you can take a vague problem, ask the right questions, and reason out loud about trade-offs without freezing.

This course works through the questions that come up repeatedly at real companies. For each one we start where the interview starts, with an ambiguous one-line prompt, and build up an answer in the order an interviewer expects to hear it.

What you build

Worked answers to the design questions asked most often in real interviews.

What you learn

• Structure an answer so you never run out of things to say
• Turn a vague prompt into concrete requirements and constraints
• Estimate scale well enough to justify your decisions
• Choose between SQL and NoSQL for a reason you can defend
• Apply caching, sharding, replication and queues where they belong
• Talk about trade-offs the way senior engineers are expected to

Before you start

• Some professional or project experience building backend systems
• Familiarity with databases, caching and HTTP