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Coding & DSA / 34
hardOpenAI

Build a time-based KV store, write three real unit tests for it, then defend a locking strategy

The OpenAI variant where the data structure is the warm-up: the round is graded on whether your tests control time and whether you can argue global vs per-key vs optimistic locking with actual reasons. Most candidates ace part one and lose the round in parts two and three.

Updated Aug 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.

The OpenAI variant where the data structure is the warm-up: the round is graded on whether your tests control time and whether you can argue global vs per-key vs optimistic locking with actual reasons. Most candidates ace part one and lose the round in parts two and three.

20 answers per topic instead of 10, plus saved progress and bookmarks · no cardor unlock all 523 remaining answers · ₹2,000 / $25
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