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Serialize a key-value store to disk when keys and values can contain any character, including your delimiter

No JSON libraries allowed, and the test data contains commas, newlines, and your escape character itself. Length-prefix encoding solves it in fifteen lines, and knowing why it beats escaping is the actual interview.

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

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