Thirty questions on what breaks when a system grows: isolation levels, sharding keys, cache invalidation, queues, and the failure each one introduces.
Thirty questions on what breaks when a system grows: isolation levels, sharding keys, cache invalidation, queues, and the failure each one introduces.
Thirty multiple-choice questions, every one of them drawn from the challenges in the Basic System Design course. They cover the ground where systems actually fail: transactions and isolation levels, connection pooling and the queries that exhaust it, sharding and what it costs to ask a question that crosses two shards, cache patterns and the stale read they eventually produce, queues, load balancer routing, circuit breakers, consistent hashing, quorum, and availability arithmetic. Most questions put you in a situation and ask what happened, or what is about to. Several hand you telemetry, a diagram, or a few lines of code and ask you to read them. Seven are straightforward, sixteen take a minute of real thought, and seven are hard. Nobody is expected to finish with all thirty. Every learner sits the same thirty questions, so one score can be compared with another.
Developers who can already build a working service and now need to reason about what happens to it under load. Backend and full stack engineers preparing for a design interview, and anyone who has finished the Basic System Design course and wants to find out what actually stuck. It assumes you have written code against a database and shipped something other people used. It does not assume you have ever run a system at scale.
30 questions, every one drawn from the course
40 minutes, timed from the first question
One pass — an answer is final once you continue
Full review afterwards: every question, your answer against the right one
English language
2 attempts per week
The timer starts on the first question and does not pause.
Each answer is final — you cannot return to a question once you continue.
Do not use search engines or seek assistance from others.
Answer each question to the best of your ability.
Your score and a full review are available immediately afterwards.
