event-driven-checkout

Event-driven checkout system built with Go microservices, NATS pub/sub, Docker, Postgres, gRPC, and grpc-gateway.

Services

1. Orders service

   • gRPC: checkout.v1.OrderService/CreateOrder
   • HTTP (grpc-gateway): POST /v1/orders
   • Persists order in orders.orders
   • Publishes orders.created

2. Payments service

   • Subscribes to orders.created
   • Mocks payment processing
   • Persists payment result in payments.payments
   • Publishes payments.succeeded or payments.failed

3. Notifications service

   • Subscribes to payment result events
   • Mocks email by logging to console
   • Persists record in notifications.notifications

Project Layout

/cmd
  /orders
  /payments
  /notifications
/internal
  /orders
  /payments
  /notifications
/pkg
  /events
  /config
  /logger
/proto
/deploy
  docker-compose.yml
/scripts
Makefile

Run with Docker Compose

make up

Send a request through HTTP -> grpc-gateway -> gRPC:

curl -X POST http://localhost:8080/v1/orders \
  -H "Content-Type: application/json" \
  -d '{"user_email":"jane@example.com","amount_cents":2599,"currency":"USD"}'

Watch logs:

make logs

Run smoke check:

make smoke

Shutdown:

make down

Protobuf Generation

checkout.proto is included under proto/checkout/v1. To generate official grpc/grpc-gateway stubs:

make proto

Requirements:

• protoc
• protoc-gen-go
• protoc-gen-go-grpc
• protoc-gen-grpc-gateway

Event Flow

1. Client calls POST /v1/orders
2. Orders service stores order and publishes orders.created
3. Payments service consumes event, stores payment result, publishes payment status event
4. Notifications service consumes payment status and stores/logs notification