Mock interview
Timed questions that you answer aloud. Think first, then compare your answer with a model answer, then score yourself against a short checklist.
How to practise
- Answer aloud. Stand up. Do not read from the page.
- State the trade-off and one number in every answer.
- Say what you would check next.
- Do not open the model answer until the timer ends or you have finished speaking.
The five-part story
Use this shape for any "tell me about a time" or incident question.
- Situation: what was happening.
- What I saw: the signals and numbers.
- What I decided, and why.
- What I got wrong.
- What I changed afterwards.
Phrases that cost points
- "It depends", without saying on what.
- "Exactly-once", without saying where it stops. A Kafka transaction does not cover a database write or an email.
- "Just add partitions", without saying that keys then move to other partitions.
- "Replication is our backup." A delete is copied to every replica.
- "We will monitor it", without naming the alert, its limit and who is paged.
An honest note. The model answers are written for this knowledge base. They are not taken from real interviews. The Kafka facts in them are as verified as the module pages they come from. A real interview also tests coding and wider system design, which this page does not.
Practice mode
Choose what to practise, then draw a question. A question does not repeat until every question in your chosen set has been used.
The mock loop ignores the filters above. It picks one concept, one trade-off, one incident and two more from design and incident questions.
Mock loop
Model answer
Score yourself
Tick each point you made aloud before you read the model answer.