Objectives

Define microservices and explain how they differ from monolithic architectures.
Identify the benefits and trade-offs of using microservices.
Understand the core components of a microservices system.
Design a basic microservices architecture for an e-commerce platform.
Prepare their local development environment for microservices development.

1. Monolithic and Microservice

1.1. Monolithic Architecture

A monolithic application is built as a single, tightly-coupled unit. All logic (user interface, business logic, data access) exists in one codebase and is typically deployed as a single executable.

Characteristics:

Single codebase and deployment unit
Shared database
Easy to develop at the beginning
Becomes harder to scale and maintain as it grows

1.2. Microservice Architecture

A microservices system is composed of multiple small, autonomous services. Each service is responsible for a specific business capability and communicates with others over a network (usually HTTP or messaging queues).

Characteristics:

Independent services, each with its own codebase and database
Services can be developed, deployed, and scaled independently
Services communicate via REST APIs or messaging queues (e.g., RabbitMQ, Kafka)

Benefits:

Scalability
Technology flexibility (different services can use different tech stacks)
Better fault isolation
Easier for large teams to work in parallel

Challenges:

Higher complexity in deployment and orchestration
Requires good DevOps and monitoring
Inter-service communication can be tricky

2. Target Architecture: E-commerce System

We will build a simplified E-commerce platform with the following microservices:

Service Name	Responsibilities	Technology
`user-service`	User registration, login, authentication	Node.js, Express
`product-service`	Product catalog management (CRUD)	Node.js, Express
`order-service`	Handles order creation, status, total price	Node.js, Express
`notification-service`	Sends notifications or logs events	Node.js, Hono
`api-gateway`	Centralized routing and authentication	Node.js, Express

Each service will have its own:

Database (MongoDB for most services)
REST API
Dockerfile for containerization

3. System Design: Architecture Diagram

The API Gateway handles all incoming requests from clients and forwards them to the appropriate service.
Each microservice handles a single responsibility and maintains its own isolated database.
Services do not directly query each other’s databases.
The Order Service communicates with the Notification Service using event-driven messaging (e.g., RabbitMQ), simulating an asynchronous flow.

4. Local Development Environment Setup

Required Tools:

Node.js
MongoDB (local or Atlas)
Postman – API testing
Docker Desktop – for containerization (used later)
VS Code or any code editor

Folder Structure Example:

/ecommerce-system/
├── user-service/
├── product-service/
├── order-service/
├── notification-service/
├── api-gateway/
└── docker-compose.yml (added in later epochs)

5. Hands-on Activity: Architecture Brainstorm

Task: In pairs or small groups, break down a well-known application (e.g., Shopee, Lazada, Amazon) into microservices.

Questions to discuss:

What are the major business functions?
Which features would become services?
How would the services communicate?

Example:

payment-service – handles transactions
review-service – manages product reviews
search-service – full-text product search
inventory-service – manages stock quantities