All public workReview scope and boundaries
Runnable seven-case receiver proof
Webhook Idempotency Acceptance Fixture
A dependency-free Node.js fixture that demonstrates how a webhook receiver can reserve an event before a side effect, acknowledge an identical retry and fail closed when delivery state is uncertain.
The engineering problem
Why this tool exists
TradingView can retry webhook delivery, networks can time out after a receiver starts work and concurrent copies can arrive before the first request finishes. Without a stable event identity and atomic reservation, one logical signal can create multiple downstream actions.
Published capabilities
- Stable event-ID reservation before the downstream side effect
- Successful duplicate acknowledgement for an identical payload
- Conflict response when an event ID is reused with changed content
- Concurrent-retry suppression while the first receipt is in flight
- Fail-closed handling for uncertain downstream completion
- Seven deterministic tests runnable with the built-in Node test runner
Engineering evidence
- Original dependency-free fixture and test source published on GitHub
- Seven deterministic cases pass without credentials, network calls or live trading
- Synthetic timeline report exposes the first duplicated side-effect boundary
- Public source states the production-persistence and crash-recovery limitations explicitly
What this case study does not claim
- The in-memory store is an acceptance fixture, not production persistence or distributed locking.
- The proof does not claim exchange acceptance, endpoint uptime, crash recovery or live-trading safety.
- A production implementation still needs a durable atomic reservation and reconciliation policy in the buyer-owned infrastructure.
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