Node.js Proposal Example (Webhooks and Duplicate Charges)

Example job situation

An ecommerce backend on Node/Express occasionally double-charges. Logs show the payment provider retrying webhooks. They want a contractor who has handled retries, not a general “I can build APIs” pitch. They asked: have you used idempotency keys?

Weak / generic proposal

Hello, I am a Node.js developer. I can build REST APIs, GraphQL, microservices, and real-time apps with Socket.io. I have 6 years of experience and I write scalable code.

I can fix your backend problems and add any features you need. Let’s get on a call today so I can start.

Why this is weak

• It never mentions webhooks, retries, or double charges.
• It offers GraphQL and Socket.io that the post did not ask for.
• It pushes an off-platform call in the first message.

Improved proposal

Hi — I would treat this as an idempotency problem on the webhook handler, not as a general API rewrite.

I have used idempotency keys on a Node/Express order service: store the provider event id, return 200 on duplicates, and only create the charge side-effect once. First step I would take here is reproducing a retry in staging with the same event payload twice and showing you the second request is a no-op.

Have you already persisted the provider’s event id anywhere, or is the handler still creating orders on every POST? And do you want failed events in a dead-letter collection we can replay, or only a unique index for now?

Why this is stronger

• It answers the idempotency question with a concrete habit, not a yes.
• The first step is diagnostic and visible to the client.
• Questions distinguish a one-line unique index from a fuller retry pipeline.

Personalization points

• Name Express, Fastify, or Nest only if they did.
• Do not promise “never double-charge again” — describe the mechanism.
• Ask which provider (Stripe, Adyen, etc.) if the post omitted it; the dashboard tools differ.

Questions you could ask

• Which payment provider is sending the webhooks?
• Is there already a unique order id from checkout?
• Staging available, or only production logs?