Microservices vs. Monolithic Architecture: A Deep Dive with Spring Boot Examples
Ekanadh Reddy
Java Full Stack Developer | IBM BPM| AWS Certified | Specialist in Spring Boot & Angular | Former Cognizant Analyst | MS in Computer Science, University of Central Missouri | LinkedIn Article Writer.
In the world of software development, choosing the right architectural style is critical to building scalable, maintainable, and efficient applications. Two prominent architectural paradigms dominate modern software engineering: Monolithic Architecture and Microservices Architecture. This article explores both approaches in depth, provides real-time examples using Spring Boot, and explains why some companies still opt for monolithic architectures despite the growing popularity of microservices
Table of Contents
1. What is Monolithic Architecture?
A monolithic architecture is a traditional software design where all components of an application (e.g., user interface, business logic, and data access) are tightly coupled and run as a single, unified process. The entire application is deployed as a single unit, typically on a single server.
Characteristics of Monolithic Architecture
Advantages
Disadvantages
2. What is Microservices Architecture?
Microservices architecture is a modern approach where an application is broken down into small, independent services that communicate over a network (e.g., via APIs). Each service is responsible for a specific business capability, has its own codebase, and can be developed, deployed, and scaled independently.
Characteristics of Microservices Architecture
Advantages
Disadvantages
3. Key Differences Between Monolithic and Microservices Architectures
4. Real-Time Example: Building an E-Commerce Application
To illustrate the differences, let’s build a simple e-commerce application with two core features:
We’ll implement this application using Spring Boot in both monolithic and microservices architectures.
4.1 Monolithic Implementation with Spring Boot
In a monolithic architecture, the entire e-commerce application (product catalog and order management) is built as a single Spring Boot application.
Step-by-Step Implementation
e-commerce-monolith/
├── src/
│ ├── main/
│ │ ├── java/
│ │ │ └── com.example.ecommerce/
│ │ │ ├── controller/
│ │ │ │ ├── ProductController.java
│ │ │ │ └── OrderController.java
│ │ │ ├── service/
│ │ │ │ ├── ProductService.java
│ │ │ │ └── OrderService.java
│ │ │ ├── repository/
│ │ │ │ ├── ProductRepository.java
│ │ │ │ └── OrderRepository.java
│ │ │ ├── model/
│ │ │ │ ├── Product.java
│ │ │ │ └── Order.java
│ │ │ └── EcommerceApplication.java
│ │ └── resources/
│ │ └── application.properties
// Product.java
package com.example.ecommerce.model;
import jakarta.persistence.Entity;
import jakarta.persistence.Id;
@Entity
public class Product {
@Id
private Long id;
private String name;
private double price;
// Getters and setters
}
// Order.java
package com.example.ecommerce.model;
import jakarta.persistence.Entity;
import jakarta.persistence.Id;
@Entity
public class Order {
@Id
private Long id;
private Long productId;
private int quantity;
// Getters and setters
}
// ProductRepository.java
package com.example.ecommerce.repository;
import com.example.ecommerce.model.Product;
import org.springframework.data.jpa.repository.JpaRepository;
public interface ProductRepository extends JpaRepository<Product, Long> {}
// OrderRepository.java
package com.example.ecommerce.repository;
import com.example.ecommerce.model.Order;
import org.springframework.data.jpa.repository.JpaRepository;
public interface OrderRepository extends JpaRepository<Order, Long> {}
// ProductService.java
package com.example.ecommerce.service;
import com.example.ecommerce.model.Product;
import com.example.ecommerce.repository.ProductRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class ProductService {
@Autowired
private ProductRepository productRepository;
public Product addProduct(Product product) {
return productRepository.save(product);
}
public Product getProduct(Long id) {
return productRepository.findById(id).orElse(null);
}
}
// OrderService.java
package com.example.ecommerce.service;
import com.example.ecommerce.model.Order;
import com.example.ecommerce.repository.OrderRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class OrderService {
@Autowired
private OrderRepository orderRepository;
public Order placeOrder(Order order) {
return orderRepository.save(order);
}
public Order getOrder(Long id) {
return orderRepository.findById(id).orElse(null);
}
}
// ProductService.java
package com.example.ecommerce.service;
import com.example.ecommerce.model.Product;
import com.example.ecommerce.repository.ProductRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class ProductService {
@Autowired
private ProductRepository productRepository;
public Product addProduct(Product product) {
return productRepository.save(product);
}
public Product getProduct(Long id) {
return productRepository.findById(id).orElse(null);
}
}
// OrderService.java
package com.example.ecommerce.service;
import com.example.ecommerce.model.Order;
import com.example.ecommerce.repository.OrderRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class OrderService {
@Autowired
private OrderRepository orderRepository;
public Order placeOrder(Order order) {
return orderRepository.save(order);
}
public Order getOrder(Long id) {
return orderRepository.findById(id).orElse(null);
}
}
// ProductController.java
package com.example.ecommerce.controller;
import com.example.ecommerce.model.Product;
import com.example.ecommerce.service.ProductService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
@RestController
@RequestMapping("/products")
public class ProductController {
@Autowired
private ProductService productService;
@PostMapping
public Product addProduct(@RequestBody Product product) {
return productService.addProduct(product);
}
@GetMapping("/{id}")
public Product getProduct(@PathVariable Long id) {
return productService.getProduct(id);
}
}
// OrderController.java
package com.example.ecommerce.controller;
import com.example.ecommerce.model.Order;
import com.example.ecommerce.service.OrderService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
@RestController
@RequestMapping("/orders")
public class OrderController {
@Autowired
private OrderService orderService;
@PostMapping
public Order placeOrder(@RequestBody Order order) {
return orderService.placeOrder(order);
}
@GetMapping("/{id}")
public Order getOrder(@PathVariable Long id) {
return orderService.getOrder(id);
}
}
# application.properties
spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
spring.h2.console.enabled=true
Observations
4.2 Microservices Implementation with Spring Boot
In a microservices architecture, the e-commerce application is split into two independent services: Product Service and Order Service. Each service has its own codebase, database, and deployment.
Step-by-Step Implementation
product-service/
├── src/
│ ├── main/
│ │ ├── java/
│ │ │ └── com.example.product/
│ │ │ ├── controller/
│ │ │ │ └── ProductController.java
│ │ │ ├── service/
│ │ │ │ └── ProductService.java
│ │ │ ├── repository/
│ │ │ │ └── ProductRepository.java
│ │ │ ├── model/
│ │ │ │ └── Product.java
│ │ │ └── ProductServiceApplication.java
│ │ └── resources/
│ │ └── application.properties
order-service/
├── src/
│ ├── main/
│ │ ├── java/
│ │ │ └── com.example.order/
│ │ │ ├── controller/
│ │ │ │ └── OrderController.java
│ │ │ ├── service/
│ │ │ │ └── OrderService.java
│ │ │ ├── repository/
│ │ │ │ └── OrderRepository.java
│ │ │ ├── model/
│ │ │ │ └── Order.java
│ │ │ └── OrderServiceApplication.java
│ │ └── resources/
│ │ └── application.properties
Product Service Implementation
server.port=8081
spring.datasource.url=jdbc:h2:mem:productdb
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
spring.h2.console.enabled=true
// OrderService.java
package com.example.order.service;
import com.example.order.model.Order;
import com.example.order.repository.OrderRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;
@Service
public class OrderService {
@Autowired
private OrderRepository orderRepository;
@Autowired
private RestTemplate restTemplate;
public Order placeOrder(Order order) {
// Check if product exists by calling Product Service
String productUrl = "http://localhost:8081/products/" + order.getProductId();
try {
restTemplate.getForObject(productUrl, Object.class);
return orderRepository.save(order);
} catch (Exception e) {
throw new RuntimeException("Invalid product ID");
}
}
public Order getOrder(Long id) {
return orderRepository.findById(id).orElse(null);
}
}
server.port=8082
spring.datasource.url=jdbc:h2:mem:orderdb
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
spring.h2.console.enabled=true
package com.example.order;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;
@SpringBootApplication
public class OrderServiceApplication {
public static void main(String[] args) {
SpringApplication.run(OrderServiceApplication.class, args);
}
@Bean
public RestTemplate restTemplate() {
return new RestTemplate();
}
}
Observations
5.1 Development Complexity
Example: In the e-commerce app, the monolithic version required one project setup, while microservices required two separate projects and REST communication setup.
5.2 Scalability
Example: In the e-commerce app, scaling the monolithic app means replicating the entire application, while microservices allow scaling only the Order Service if order volume spikes.
5.3 Deployment
Example: In the e-commerce app, updating the Product Service in the monolithic app requires redeploying everything, while in microservices, only the Product Service is redeployed.
5.4 Fault Isolation
Example: In the e-commerce app, a memory leak in the Order Service would crash the monolithic app but only affect the Order Service in the microservices setup.
5.5 Technology Flexibility
Example: In the e-commerce app, the monolithic app is locked into Spring Boot, while microservices could use Spring Boot for Product Service and Python for Order Service.
6. Why Some Companies Still Prefer Monolithic Architecture?
Despite the hype around microservices, many companies, especially startups and small-to-medium enterprises, continue to use monolithic architectures. Here are the key reasons, explained step-by-step:
6.1 Simplicity in Development and Maintenance
6.2 Lower Operational Overhead
6.3 Faster Initial Development
6.4 Easier Debugging and Testing
6.5 Cost-Effectiveness for Small-Scale Applications
6.6 Gradual Transition to Microservices
6.7 Legacy Systems and Team Expertise
7. Conclusion
Both monolithic and microservices architectures have their strengths and weaknesses, and the choice depends on the specific needs of the project, team, and organization. Monolithic architectures are ideal for small-to-medium applications, startups, or projects requiring simplicity and fast development. Microservices, on the other hand, excel in large-scale, complex applications where scalability, fault isolation, and team autonomy are critical.
Using the Spring Boot e-commerce example, we demonstrated how a monolithic application is simpler to build and deploy but less flexible, while a microservices approach offers scalability and independence at the cost of complexity. Some companies continue to prefer monolithic architectures due to their simplicity, lower operational overhead, and suitability for smaller applications or early-stage products.
Ultimately, the decision should be based on factors like team expertise, project scale, budget, and long-term goals. A well-designed monolithic application can serve as a solid foundation, with the option to evolve into microservices as the business grows.
8. References
Thank you
EKANADHREDDY KAKULARAPU