The customer's team has to live with this API for years, on a schedule you don't control. The interview is about how you ship changes without a 2 a.m. page on their side.
Updated Aug 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.
The customer's team has to live with this API for years, on a schedule you don't control. The interview is about how you ship changes without a 2 a.m. page on their side.
The senior signal is treating backward compatibility as the central constraint: additive-only changes, never-remove-without-a-version, and expand-contract for breaking changes. Strong candidates pick REST for an integration API a third party adopts and reserve GraphQL for cases with many client-shaped reads. Watch for offset pagination proposed without noticing it breaks on concurrent inserts; push toward cursor pagination. Probe with 'you must rename a field' to test whether they break clients or add-then-deprecate.
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