Imagine you’re building an e-commerce website. Initially, it’s pretty simple: a product management feature, a user management feature, and an order fulfillment feature. All wrapped up in a single application – we call this a monolithic architecture . At first, this model works well, and is easy to develop and deploy.
However, as your business grows, traffic increases, the number of products increases, and the development team grows. At this point, the monolithic application begins to show major limitations. A small change in the product management section also requires you to test and redeploy the entire system, which can risk affecting other parts. If the order processing function is overloaded during a promotional season, you have to duplicate (scale) the entire application, including the less used functions, wasting resources. Applying a new technology for a specific feature also becomes difficult because the entire system is sharing the same technology stack. This is when we need to find a more flexible architectural solution - that is microservices .
Microservices architecture is a software development approach in which a large application is composed of many small, independent services. Each of these services runs in its own process and communicates with other services through lightweight mechanisms, typically HTTP/REST-based APIs (Application Programming Interfaces) or message queues.
Going back to the e-commerce site example. Instead of a monolith, we'll break it down into specialized services:
Each of these services can be developed, deployed, and scaled independently. They are like specialized departments within a large organization, each managing its own work but still working together to achieve a common goal.
Adopting a microservices architecture brings many significant benefits, especially for large and complex systems:
This is one of the big advantages. With monoliths, you have to scale the entire application. With microservices, you only need to scale the services that are under high load. For example, during the sales season, Order Service and Payment Service may need 5-10 times more resources, while User Service may need only a small increase or none at all. This helps optimize resource costs and ensure performance for each part of the system.
In a monolithic system, a failure in a less important function can bring the entire application down. With microservices, if the Recommendation Service fails, core services like the Product Service or Order Service can still function normally. Users may not see product recommendations, but they can still browse and make purchases. This greatly improves the user experience and reliability of the system.
Each microservice can be built using the programming language, framework, or database that best suits its function. For example, a Product Service might use Java and PostgreSQL for its stability and transaction handling capabilities, while a Recommendation Service might use Python with machine learning libraries and a NoSQL database like MongoDB for efficient unstructured data processing. This allows teams to choose the best tool for the job without being constrained by a common technology stack.
Since services are independent, one team can update and deploy the Product Service without affecting or having to wait for other teams. This shortens the development cycle and increases time-to-market. CI/CD (Continuous Integration/Continuous Deployment) processes become more efficient when applied to each small service.
Microservices architectures are often associated with small development teams focused on one or a few specific services. These teams have greater autonomy over technology and workflow choices, which increases ownership and accountability. This is consistent with Conway’s Law – the structure of a software system reflects the communication structure of the organization that created it.
Each microservice has a narrower scope of functionality and a smaller codebase than a large monolithic application. This makes it easier for new developers to access, understand, and maintain the code of each service. Debugging also becomes more focused.
Real-world example: Think of Netflix or Amazon. They can’t operate at global scale with a single monolithic application. Netflix has hundreds of microservices that handle everything from video streaming, to account management, to content recommendations, to video encoding. Each service is managed by its own team and can be updated multiple times a day without disrupting the viewer experience.
Despite the many benefits, microservices architecture also comes with significant challenges that require careful preparation:
Managing a system of microservices is much more complex than a single monolithic application. You need robust tools and processes for deployment, monitoring, logging, and service discovery. Technologies like Docker (containerization) and Kubernetes (orchestration) are often used to solve this problem, but they also require specialized knowledge and skills.
Services need to communicate with each other. This can be done via synchronous API calls or asynchronous message queues. Both approaches have potential issues such as network latency, network errors, and error handling when a service fails to respond. Mechanisms such as circuit breakers, retries, and timeouts are required.
In monolith, you typically have a centralized database. With microservices, each service typically has its own database to ensure independence. This leads to challenges in data consistency across the system. Transactions spanning multiple services become complex, requiring design patterns like Sagas or ensuring eventual consistency.
Testing a single microservice (unit test, integration test) can be simple. However, comprehensive testing (end-to-end testing or E2E testing) for the entire system where services interact with each other becomes much more difficult. A thorough testing strategy and a robust staging environment are required.
To be successful with microservices, an organization needs a strong DevOps culture where Development and Operations teams work closely together. Automation is key.
Microservices are not the right solution for every problem. Choosing this architecture requires careful consideration:
Consider microservices when:
Maybe you don't need microservices yet (or should start with "monolith first"):
Microservices architecture has proven its value in building modern, flexible, and highly scalable software systems. It allows organizations to innovate faster, improve system resilience, and optimize resource utilization. However, migrating to microservices is not simple and requires investment in tools, processes, and team skills.
For developers, it is important to understand both the advantages and disadvantages of microservices, as well as when to adopt them. There is no perfect solution for every situation, and choosing the right architecture depends on the specific context of the project and organization. Starting with a well-structured monolith and then gradually migrating to microservices as needed is often a sound strategy for many projects.