Monolith to Microservices — Evolution example

This repository demonstrates the progression from a monolithic architecture to a fully distributed microservices system. Each folder represents a different architectural stage:

Folder Overview

• 01_monolith/ — Single monolithic application with all logic in one file
• 02_modulith/ — Modular monolith: still a single process, but organized into logical service modules
• 03_microservices/ — Fully distributed microservices: independent services, separate processes
• microservices/ — Additional microservices examples or helper modules

Architecture Stages

Stage 1: Monolith (01_monolith/)

Single file, single process. Everything together.

cd 01_monolith
node index.js

Stage 2: Modulith (02_modulith/)

Still a single process and entry point, but code is organized into separate logical modules (services):

• data-service.js
• aggregation-service.js

cd 02_modulith
node index.js

Stage 3: Microservices (03_microservices/)

Each service runs in its own process. Services communicate over the network (HTTP, etc.).

cd 03_microservices
npm install
npm run start

Quick Start — Run the final microservices setup

From the root of this repository:

cd 03_microservices
npm install
npm run start

This starts the full microservices demo (usually on http://localhost:3000 or similar). Check the server output for the exact URL.

Prerequisites

• Node.js
• npm

Learning Notes

• Review each stage in order to understand the architectural evolution
• 01_monolith/ shows the original single-file design
• 02_modulith/ shows internal organization without distributed architecture
• 03_microservices/ shows how to split into separate processes and services
• Each stage uses plain JavaScript with minimal dependencies (Express, axios, etc.)

Additional Resources

• Review package.json in each folder for dependencies and scripts
• Check serve.js in 03_microservices/ for the orchestration logic
• Inspect services/ folders to see service implementations