Broken code. Fix it. 10
Production bugs with the artifacts you'd see on call — failing test, log excerpt, broken code. Identify the root cause, fix it, compare against the canonical solution.
Order pagination returns duplicate rows
freeThe /orders endpoint returns the same order on two consecutive pages. Find the off-by-one and fix it.
Ledger drift after refund retry
freeA refund retry occasionally produces a ledger entry where the refund is recorded twice but the wallet was credited once. Find the bug and fix it.
Click-tracking counter drops events under load
freeClick-tracking endpoint occasionally undercounts events. Some events vanish, others crash the concurrent handler that increments. Find the bug and fix it.
Validation endpoint p99 climbs under load
proThe /validate endpoint's p99 latency climbs from 8ms to 280ms once traffic crosses 500 RPS. Find the hot-path waste and fix it.
Daily summary email arrives on the wrong day
proUsers complain that their "yesterday's activity" email shows today's data, or skips a day entirely. Find the timezone bug.
JWT verification accepts forged tokens
proSecurity team filed a P1: an attacker can forge admin tokens against the auth middleware. Find the verification flaw and fix it.
Worker pool leaks background workers on shutdown
proA worker pool that processes background jobs leaks background workers on every service restart. Find what's wrong with the lifecycle.
User profile endpoint accepts privilege escalation
proPATCH /users/me lets a regular user upgrade themselves to admin by sending `{"role": "admin"}` in the body. Find the mass-assignment flaw and fix it.
Background-task spans become orphans in tracing
proDistributed traces show order-creation as a clean parent span, but the email-send and audit-log operations dispatched after the order appear as detached root spans with no parent. Find the propagation bug.
Idempotency cache returns the wrong customer's response
proCustomer A submits a charge. Customer B submits a charge a few minutes later and gets back Customer A's payment confirmation. Find the cross-tenant leak in the idempotency layer.