System designEasysd-g549

Subject Feature flagsLevel Entry–Mid~25 minCommon in Distributed systems interviewsIndustries Software development, Technology

Question

Design a feature-flag toggle store for a single web application. Engineers want to turn features on/off (and roll out to a percentage of users) without redeploying. Flags are read on almost every request to decide which code path to take; they're changed only occasionally by humans through an admin page. Describe the storage and how the app reads flags fast.

What a strong answer looks like

Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts — data model, bottlenecks, consistency, failure modes — and name the trade-offs you are making.

Learn the concepts

Narrate your design

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Run or narrate your approach, then ask the coach.