Mock system design interview at Confluent
A live 45-minute round on a question reported in Confluent interviews, run by an AI interviewer that asks one thing at a time, probes what you say, looks at your whiteboard, and weighs what that round is reported to weigh. It ends with a debrief: a score, what was strong, what was missing.
Design a Distributed Message Queue
A Kafka-style log that ingests a million messages a second, keeps them in order per key, replicates them so no acknowledged message is lost, and lets many consumer groups read at their own pace.
You will not see the requirements, the numbers or the design before you start. That is the point.
What the Confluent round is reported to look like
About an hour, and loops for experienced engineers often include two design rounds. Reported prompts are mostly product-shaped rather than about streaming: a podcast service, an RSS feed reader, a temporary email service or a news feed.
What it weighs
- API design in detail, down to verbs, status codes and headers
- A data model, and the SQL queries behind each feature
- Scale follow-ups: sharding the database and cache, with estimates for requests, memory and servers
- Tradeoffs you can defend when pressed
The common mistake
Preparing only for Kafka internals. Candidates mostly report product prompts such as a podcast or feed service, where the questions go to the API, the tables and the queries, so be ready to write those out rather than only draw boxes.
From public interview guides and candidate reports, and Confluent’s own interview guidance where it publishes any. Not endorsed by Confluent. The interviewer is an AI running in that style; it is practice, not a prediction.
Start the round
The interviewer’s opening question is free. Answering it is part of Pro. See an example round and its debrief →
The 2 questions this round draws from
Each is reported in Confluent interviews. Pick one to sit, or read its reference design and walk through a strong answer first.
- Design a Distributed Message QueueA Kafka-style log that ingests a million messages a second, keeps them in order per key, replicates them so no acknowledged message is lost, and lets many consumer groups read at their own pace.drawn
- Design a Distributed Logging SystemCollect 10 million log lines a second from 100,000 hosts, make them searchable within seconds, stream them live, and keep a year affordably.
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