Console
Send the same key twice on purpose and watch the response stay identical.
Log
All charges (shared)
API reference
POST /api/scenarios/idempotent/charges
header Idempotency-Key: <any string>, body { amount } → { charge } (201 first time, 200 on replay)
GET /api/scenarios/idempotent/charges
→ every charge ever created — use it to confirm a replay did NOT add a second entry
curl -X POST https://playground.krishanchawla.com/api/scenarios/idempotent/charges -H "Content-Type: application/json" -H "Idempotency-Key: abc-123" -d '{"amount":49.99}'
curl -X POST https://playground.krishanchawla.com/api/scenarios/idempotent/charges -H "Content-Type: application/json" -H "Idempotency-Key: abc-123" -d '{"amount":49.99}' # same key, same response