GO TO A SECTION

↑ ↓ to navigate · Enter to openExplore all sections →
FDEInterviews logo
← System Design & Production Engineering / 45
medium★ EssentialStripeRetoolVercel

Design the integration API a customer's engineers can adopt without it breaking on them: REST vs GraphQL, versioning, pagination.

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.

20 answers per topic instead of 10, plus saved progress and bookmarks · no cardor unlock all 548 remaining answers · ₹2,000 / $25

Every answer, concept and course, every paper breakdown, all published video lessons, hands-on FDE Lab missions, Premium PDF guides and companion files, the full practice-test bank and work-sample downloads. Referral Premium excludes guide PDFs and their companion files.

6 months · One payment · No auto-renewal

Study alongside free video lessons.

Course lessons in this topic

Keep practising

Next in this trackHow do you design a customer deployment so their team can run it without you, and you make yourself obsolete?PremiumNext in this trackDesign a real-time collaborative coding assistant: stream completions under 200ms for 10k concurrent usersPremiumNext in this trackDesign a safety-enforced LLM API gateway: intercept prompts and outputs, apply dynamic policy, add under 5% latency, support streamingPremium
FEDITOR'S NOTE

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.

DISCUSSION · 0

No comments yet — be the first to share your approach.