apisEASYAPI CHALLENGE
Warm up with idempotency key design diagnostic drill
Easy APIs arena: safe retries, request hashes, and conflict responses
XP reward
145
Coins
12
Target time
45m
A learner is about to attempt the full idempotency key design arena. Build a smaller but realistic diagnostic that exposes whether they understand safe retries, request hashes, and conflict responses. You are working inside an API platform team, and the arena only clears when the result is safe, deterministic, and explainable.
Learning objective
Learn to apply safe retries, request hashes, and conflict responses in an API platform team while explaining the invariant, safety constraints, and hidden edge cases.
Mission order
POST /charges accepts amount, currency, customer_id, and Idempotency-Key. Include one normal case, one malformed case, and one ordering or safety edge case. Implement the direct solution first, then document the one edge case that can break it. Submit the solution plus enough reasoning to pass hidden edge cases.Visible checks
selects the safest option
Expected: B
includes justification
Expected: mentions correctness or risk
Clear requirements
- Demonstrates safe retries, request hashes, and conflict responses
- Handles the visible sample and hidden edge cases
- Keeps output deterministic and explainable
- Avoids unsafe dynamic execution
Secure validation contract
Judge type
API CHALLENGE
Complexity target
Contract remains stable under retries, pagination, errors, and abuse cases
Workspace
Code editor
typescriptsafe mock judge
Charging editor core
Test Results
Run the visible checks when your first pass is ready.
Clear Protocol
1Read the scenario and restate the expected output shape.
2Run visible checks before chasing hidden edge cases.
3Use Genie for one nudge if stuck, then explain the invariant.
4Submit only when the result is deterministic and safe.
Rewards
XP
145
Coins
12
Mission Route
Hints
Hints are metered and logged for No Hint Hero runs.
Genie Mentor Core
Hint protocol / contextual guardrails active
Progressive hints
Failed-test aware
Solution guarded
Mission: apis-easy-idempotency-key-diagnostic0 attempts0 failed tests0 hints used
Progressive hint depth
Genie: Genie online. I use your mission, attempts, failed tests, hints, and path context to coach the next rep without dumping answers first.