Our Stripe Delivery Pipeline — From Checkout to Download in 30 Seconds

When someone buys from Whoff Agents, they get their product in under 30 seconds. No manual fulfillment. No waiting for a human to check Stripe.

Here is exactly how the pipeline works.

The Flow

Stripe Checkout → Webhook → Atlas listener → File delivery → Email receipt

Total time: ~28 seconds on average.

Step 1: Stripe Webhook

We listen to checkout.session.completed. The moment Stripe fires it, our webhook handler wakes up.

We validate the signature (stripe.webhooks.constructEvent) before doing anything. Security first.

const event = stripe.webhooks.constructEvent(
  req.body,
  sig,
  process.env.STRIPE_WEBHOOK_SECRET
);

if (event.type === "checkout.session.completed") {
  await handlePurchase(event.data.object);
}

Step 2: Customer Record Creation

handlePurchase does four things:

Extracts customer email and product ID from the session
Creates a customer record in our flat-file database
Generates a time-limited download token (24hr expiry)
Queues the delivery email

We use flat files, not Postgres. For our current volume, it is faster to set up and easier for Atlas to read/write autonomously.

Step 3: Download Token

The token is a signed JWT:

const token = jwt.sign(
  { customerId, productId, email },
  process.env.JWT_SECRET,
  { expiresIn: "24h" }
);

const downloadUrl = `https://whoffagents.com/download?token=${token}`;&ref=devto-3507661

The download endpoint validates the token, logs the access, and serves the file.

Step 4: Delivery Email

Resend handles the email. Template is simple: product name, download link, expiry notice, support email.

await resend.emails.send({
  from: "deliver@whoffagents.com",
  to: email,
  subject: `Your ${productName} is ready`,
  html: deliveryTemplate({ name, downloadUrl, expiresAt })
});

Total email delivery time: 2-4 seconds.

What We Learned Building This

Webhook validation is non-negotiable. Skip it and anyone can POST fake events to your endpoint and trigger free downloads. We got this right on day one.

Idempotency matters. Stripe can fire the same webhook twice. Our handler checks if a customer record already exists before creating one. No duplicate deliveries.

Flat files beat a database at launch scale. We can serve 100 customers without spinning up Postgres. When we hit 1,000, we will migrate. Until then, files are faster to ship and Atlas can read them directly.

Test with Stripe CLI before going live. stripe listen --forward-to localhost:3000/webhook lets you fire real test events locally. We caught 3 bugs this way.