NestJS gRPC Microservices

A production-style proof of concept demonstrating gRPC inter-service communication using NestJS in a monorepo layout.

Architecture

                         +---------------------+
                         |      Client          |
                         |  (curl / browser)    |
                         +----------+-----------+
                                    | HTTP
                                    v
                  +-------------------------------+
                  |        API Gateway            |
                  |     (NestJS - port 3000)      |
                  |                               |
                  |  GET/POST /users              |
                  |  GET/POST /orders             |
                  +------+---------------+--------+
                         |               |
                   gRPC  |               |  gRPC
                         v               v
          +------------------+  +------------------+
          |   User Service   |  |  Order Service   |
          |  (port 5001)     |  |  (port 5002)     |
          |                  |  |                  |
          |  In-memory store |  |  In-memory store |
          +------------------+  +------------------+

Why gRPC over REST for inter-service communication?

Concern	gRPC	REST (JSON)
Serialization	Protocol Buffers (binary) -- smaller payloads, faster encode/decode	JSON -- human-readable but verbose
Latency	HTTP/2 multiplexing, persistent connections, binary framing	HTTP/1.1 typically, text-based
Type safety	.proto contract shared across services; codegen guarantees type alignment	OpenAPI/Swagger optional, runtime validation
Streaming	Native bidirectional streaming built into the protocol	SSE or WebSocket bolted on
Code generation	First-class codegen for 10+ languages from a single .proto file	Manual client/server code or third-party generators

For internal service-to-service calls where human readability is not required, gRPC delivers measurably lower latency and stronger compile-time guarantees.

Prerequisites

• Docker and Docker Compose
• (Optional) Node.js 20+ and npm for local development

Quick start

# Build and start all services
docker-compose up --build

# In another terminal, test the endpoints
curl http://localhost:3000/users
curl http://localhost:3000/orders

API endpoints

Method	Path	Description
GET	/users	List all users
GET	/users/:id	Get a user by ID
POST	/users	Create a user ({ "name": "...", "email": "..." })
GET	/orders	List all orders
GET	/orders/:id	Get an order by ID
POST	/orders	Create an order ({ "userId": "...", "product": "...", "quantity": 1, "price": 29.99 })

Local development (without Docker)

# Install dependencies
npm install

# Build all services
npm run build

# Start each service in separate terminals
npm run start:user-service
npm run start:order-service
npm run start:api-gateway

When running locally, update the gRPC client URLs in the gateway modules to point to localhost instead of the Docker service names.

Project structure

.
+-- proto/                          # Shared protobuf definitions
|   +-- user.proto
|   +-- order.proto
+-- apps/
|   +-- api-gateway/src/            # HTTP entry point
|   |   +-- main.ts
|   |   +-- app.module.ts
|   |   +-- user/
|   |   +-- order/
|   +-- user-service/src/           # gRPC server for users
|   +-- order-service/src/          # gRPC server for orders
+-- docker-compose.yml
+-- Dockerfile
+-- nest-cli.json
+-- package.json
+-- tsconfig.json