Every data migration at every customer site needs this exact tool, which is why Palantir and Retool keep asking it. The diff is a dict comparison; the grade hides in keys, duplicates, and column drift.
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Build a CSV diff tool: report added, removed, and changed rows between two files, with composite keys
Every data migration at every customer site needs this exact tool, which is why Palantir and Retool keep asking it. The diff is a dict comparison; the grade hides in keys, duplicates, and column drift.
Updated Aug 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.
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Next in this trackBuild a versioned key-value store: put/get, plus get(key, timestamp) for historical readsNext in this trackBuild a rate limiter: fixed window, then sliding window, then per-customer tiersNext in this trackYou're given a small repo with failing tests and a vague bug report: fix the bugs, then add a feature
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