Real World Example

At a payment gateway like Razorpay, a "create payment" request passes through many layers. Mapped to NestJS:

Stage	What it does for `POST /v1/payments`
Middleware	Assign `x-request-id`, log the request, parse raw body for signature checks
Guard 1: `ApiKeyGuard`	Check the merchant's API key and secret
Guard 2: `ThrottlerGuard`	Max 100 requests per second per merchant
Interceptor: `IdempotencyInterceptor`	Same `Idempotency-Key` twice? Return the first response
Pipe: `ValidationPipe`	Amount is an integer in paise, currency is INR
Handler + services	Create the payment, call the bank/UPI switch
Interceptor (after)	Wrap response, record latency metric
Filter	Bank timeout becomes `502 {"error":{"code":"GATEWAY_ERROR"}}`

Example

curl -i -X POST https://api.shopease.in/v1/payments \
  -H "Authorization: Bearer sk_live_xxx" -H "Idempotency-Key: 7f1c-22" \
  -H "Content-Type: application/json" -d '{"orderId":"ORD-7781","amount":129900,"currency":"INR","method":"upi"}'

Example output

HTTP/1.1 201 Created
X-Request-Id: 0b9a5c1e
X-Response-Time: 182ms

{"data":{"paymentId":"pay_N8kq2","status":"created","amount":129900,"currency":"INR"}}

A Payment API Request in Production

Example