System design interview question
"Design a feature store. Machine-learning models need features — 'this user's purchases in the last 30 days', 'this merchant's fraud rate' — both when training offline and when serving online in a few milliseconds. The same feature must mean the same thing in both places. Hundreds of models, thousands of features."
training–serving consistency, which is the defining problem of ML infrastructure and is almost invisible until it causes a silent production failure. The distinguishing content is: why the same feature computed twice diverges, what point-in-time correctness means and why getting it wrong inflates offline metrics, and the dual-store architecture that follows.
On Practick another engineer interviews you live for 60 minutes on a question from this bank. They have the full interviewer guide beside the call: the answers to your clarifying questions, the numbers to hand out, a ladder of follow-ups and a scoring rubric. You get the model solution once the session settles. It is free: interview someone for an hour and you have earned your own.
Book a free mock interviewAll 132 system design interview questions
System design mock interviews · DSA interview questions · Free mock interview practice · Browse interviewers · Sign in