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In today’s tech-drive](medium.com/@mauryavishal/list/system-design.. world, software architecture plays a crucial role in determining the efficiency, scalability, and maintainability of applications. Two common architectural approaches are Monolithic Architecture and Microservices Architecture. Let’s explore these concepts in simple terms, along with their pros, cons, and real-world examples.
What is Monolithic Architecture?
Monolithic architecture is like running a small, family-owned restaurant where everything happens under one roof. From taking orders to cooking, billing, and managing inventory—it’s all handled in one space.
In software terms, a monolithic application is a single, unified system where all functionalities (e.g., user authentication, order management, billing, etc.) are bundled together.
Example: Imagine an online store. In a monolithic setup, everything from managing the product catalog to processing payments exists in one application.
Advantages of Monolithic Architecture
Simplicity: Easy to develop and deploy initially.
Performance: Since everything runs within a single process, communication between components is faster.
Centralized Testing: Testing and debugging are straightforward as the codebase is in one place.
Disadvantages of Monolithic Architecture
Scalability Issues: Scaling a specific part (e.g., the payment system) requires scaling the entire application, leading to inefficiency.
Complex Maintenance: As the application grows, the codebase becomes harder to manage, debug, and deploy.
Single Point of Failure: A bug in one module can bring down the entire application.
Slow Deployment: Any change requires redeploying the whole application.
What is Microservices Architecture?
Microservices architecture is like a food court where different vendors manage specialized tasks. One vendor handles desserts, another serves pizza, and a third provides drinks. Each works independently but contributes to the overall customer experience.
In software, microservices break down a large application into smaller, independent services that handle specific business functions (e.g., user management, order processing, payment handling). These services communicate with each other via APIs.
Example: For an online store, microservices might include separate services for product inventory, user authentication, order management, and billing.
Advantages of Microservices Architecture
Scalability: Each service can be scaled independently. If order processing needs more resources, only that service is scaled.
Flexibility: Different technologies can be used for different services based on their requirements.
Fault Isolation: A failure in one service (e.g., billing) doesn’t bring down the entire application.
Faster Development: Teams can work on different services simultaneously without interfering with each other.
Disadvantages of Microservices Architecture
Complexity: Managing and deploying multiple services is challenging, especially as the number of services grows.
Inter-Service Communication: Requires robust mechanisms to handle communication between services, leading to potential latency issues.
Transaction Management: Distributed systems make it harder to maintain ACID (Atomicity, Consistency, Isolation, Durability) properties across multiple databases.
Monitoring and Debugging: Identifying the root cause of issues across services can be time-consuming.
Real-World Examples
Monolithic Architecture:
Startups or Small Businesses: Many small companies initially use monolithic architecture due to its simplicity.
Example: Early versions of applications like eBay or LinkedIn started as monolithic systems before transitioning to microservices.
Microservices Architecture:
Netflix: Each feature (like recommendations, user profiles, and streaming) is a separate microservice. This allows Netflix to scale its services globally.
Amazon: Breaks its e-commerce platform into services like search, payment, and delivery. This division ensures fast, independent updates.
How to Divide a Service into Microservices
Breaking a monolithic application into microservices isn’t random—it follows a structured approach. Here are the phases and patterns that guide this process:
Phases of Microservices Division
Decomposition: The first step is breaking the application into smaller pieces. This can be done in two ways:
By Business Functionality: Identify core business functionalities like order management, billing, and product management and create services for each.
By Subdomain: Use Domain-Driven Design (DDD) to identify larger domains (e.g., order management) and further split them into subdomains (e.g., order placement, order tracking).
Database Segmentation: Each microservice ideally has its own database to remain independent. Alternatively, a shared database can be used initially but should evolve into isolated ones for better scalability.
Communication: Microservices communicate using APIs (REST or gRPC) or asynchronous methods like events. Choosing the right communication method ensures smooth integration between services.
Integration: Use patterns like API Gateways to manage requests between the client and multiple services. This simplifies how external systems interact with microservices.
And so on, there are many phases depending on the application we are creating. Selecting the appropriate pattern is crucial as it defines how our microservices will operate. For now, let’s take a closer look at Decomposition, leaving the other phases for upcoming discussions.
Decomposition of a service
By Business Functionality/Capability
In this pattern, the application is divided into services based on core business functionalities or capabilities.
Example:
Consider an e-commerce application:
Order Management Service: Handles order placement, cancellations, and tracking.
Payment Service: Processes transactions and refunds.
Inventory Service: Manages stock levels and updates.
User Management Service: Manages user authentication, profiles, and roles.
Each service represents a business capability and operates independently. For instance, if the "Payment Service" is upgraded, it does not affect the "Order Management Service," ensuring modularity and flexibility.
By Subdomain (DDD)
In this pattern, the application is broken down based on subdomains. This involves identifying larger domains within the application and further splitting them into smaller, cohesive units.
Example:
In the same e-commerce application, the Order Management domain can be divided into subdomains:
Order Placement Service: Handles new orders.
Order Fulfillment Service: Manages processing, packing, and shipping.
Order Tracking Service: Allows users to track their orders in real time.
Using the subdomain pattern, each smaller service is focused on a specific part of the domain, ensuring a clear separation of concerns.
Conclusion
Choosing between Monolithic and Microservices Architecture depends on the scale, complexity, and goals of your application. Monolithic systems are simpler to build and maintain for small-scale applications, while microservices offer scalability, fault tolerance, and flexibility for larger, complex systems. To provide a quick overview, here’s a comparison table:
| Feature | Monolithic Architecture | Microservices Architecture |
| Codebase | Single, unified | Multiple, independent services |
| Scalability | Difficult | Easy to scale individual services |
| Deployment | Entire application redeployed | Services deployed independently |
| Fault Isolation | Low | High |
| Complexity | Simple initially | More complex to manage |
| Examples | Traditional banking systems | Netflix, Amazon, Uber |
The key is to align your architectural choice with your business needs, keeping future growth and maintenance in mind.