In the web development industry you hear more and more about microservices, an approach to building large applications by splitting them into small, mutually independent services. They allow greater flexibility, faster development and more effective scaling. At the same time, like every architecture, microservices have their weak points and pitfalls – rolling them out requires a well thought out strategy and the right tools. In a world of rapidly changing business conditions, extensive online services and rising user expectations, this approach is becoming crucial for many companies, because it enables efficient resource management and quick reactions to changes in the market environment. In this article we take a look at what microservices actually are, which problems they solve and which new challenges they can bring into projects. You will also learn in which situations microservices turn out to be particularly beneficial and why in some cases the traditional monolithic architecture can still be the better choice.
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What is microservice architecture about?
In traditional monolithic applications the whole business logic and all functionality are concentrated in one code structure that runs as a single, coherent process. This means that even small changes in one module can affect the stability or performance of the entire application. Microservices, on the other hand, are a series of small, separated services, each of which handles a specific function (for example authentication, payment handling, product catalog management) and communicates with the other services through network protocols or queues.
The usual assumption is that microservices are deployed independently and may use different technologies. As a result each development team has more freedom in choosing its tools and can decide independently when to release the next version of its service. Such a split eliminates the bottleneck problem typical of a monolith, where request processing slows down inside one large process.
The microservice approach relies on the idea of horizontal scaling, which means that instead of increasing the computing power of a single server (vertical scaling), you can run more copies of specific microservices, for example in the cloud. Apart from better use of resources, this also gives greater resilience to failures: if one service stops working, the rest of the application can still operate correctly.
Advantages of microservices: flexibility, scalability and fast delivery
One of the main reasons why companies decide to use microservices is flexibility and the ability to develop individual parts of the system independently. Each microservice can be updated at its own pace without worrying about compatibility with the remaining modules, as long as the interfaces and dependencies are properly defined.
Another important advantage is ease of scaling. In the case of heavy traffic or seasonal peaks (for example in e-commerce before the holidays), you can launch additional instances of the microservice responsible for the most heavily loaded areas of the system without investing in expanding the whole application. As a result, server resources are used more efficiently.
Microservices also support faster delivery of new features, because you modify a narrower slice of code than in a monolithic architecture. Small services are by nature easier for development teams to understand and test, which helps reduce the complexity of the project.
Challenges and difficulties in microservice projects
Although the vision of independent services sounds attractive, it is worth remembering that microservices introduce an additional layer of complexity. In a monolith, communication between modules happens internally, while in microservices it is based on network protocols (HTTP, gRPC, AMQP and so on). That means you have to manage the network properly, configure endpoints and handle errors on the client side.
You also have to be ready for a more extensive infrastructure, often in the form of containerization (Docker, Kubernetes) and orchestration mechanisms. A microservice application has more points at which a failure can occur (for example one microservice becoming unavailable), which calls for retry mechanisms, circuit breakers and monitoring tools (Prometheus, Grafana).
Testing and debugging also become more complicated, especially when you need to run several services in the development environment. Some companies therefore decide to stay with a monolithic architecture (or with a hybrid), because in their case the advantage of microservices is not that significant compared with the growing number of dependencies.
Microservice use cases
Microservices work best in situations where:
- The project is growing rapidly
If we know that our system will be heavily expanded in the future and we need to introduce changes quickly in different areas, microservices can make the work easier and help avoid chaotic code. - The team is split into many specialized groups
The ability to separate individual services is an advantage when teams can work almost independently, choosing their own technologies and development strategies. - High scalability is required
For services with a rapidly growing number of users, microservices open a simple path to scaling (for example a separate cluster for the microservice that handles payments). - Reliability is critical
A fault in a single service does not have to bring down the whole system, which translates into a higher level of availability and a lower risk of losses.
On the other hand, if we are building a small application with a limited scope and we rarely introduce changes, it may turn out that a monolithic architecture is the more economical choice.
Inter-service communication and integration strategy
In microservices, the way services communicate with each other is particularly important. The most popular approaches are:
- RESTful API: Using the HTTP protocol to exchange messages. Simple to implement and widely supported by tools.
- gRPC: An approach based on the HTTP/2 protocol and the Protobuf format, which provides fast and efficient transmission. Particularly attractive when there are many calls between services.
- Message queues (MQ): Examples include RabbitMQ and Apache Kafka. They work well when we want looser coupling between services and asynchronous request processing.
The choice of a specific method depends on the nature of the application and the frequency of calls. In distributed systems with a large number of interactions, the asynchronous approach can bring major benefits by minimizing the delays caused by waiting for responses.
Monitoring and maintaining a microservice application
Because of the number of components, monitoring takes on primary importance in microservices. In practice, logging events is no longer enough; you need more advanced tools that let you track the flow of requests through successive services. So-called distributed tracing (for example Jaeger, Zipkin) makes it possible to understand at which point in the system the delay appears.
Analyzing performance metrics is just as important, for example response time, memory usage or the number of handled requests. This lets you react in time to a growing overload or unexpected errors. Finally, an alerting system should signal when a service stops responding or the number of failed requests rises above a defined threshold.
From the administration point of view, microservices often go together with DevOps practice and containerization. Environments such as Docker, Kubernetes or AWS ECS make it easier to manage many services and to make sure that every microservice is available in the required number of instances.
Best practices for rolling out microservices
- Start with a small slice
Do not try to break the whole monolithic application into a dozen or more microservices right away. It is better to separate a single piece of functionality and check how such a model works in practice. - Define clear service boundaries
Every microservice should have a clearly defined responsibility and must not duplicate the logic of another service. The concept of a bounded context from Domain-Driven Design helps here. - Keep interfaces stable
When the client requires a fixed API contract, introducing changes in a service becomes much easier, because it removes the risk of breaking the remaining parts of the system. - Automate tests and deployments
With a large number of services, manual testing can be a nightmare. Take care of continuous integration and deployment (CI/CD), including end-to-end tests. - Provide proper monitoring tools
Without insight into the current state of the services, problems may be detected too late, which translates into a loss of user trust.
Microservices are not just a fashion, but above all an architecture that allows a better fit to rapidly changing market requirements and business needs. They let you design applications that are more scalable, more modular and more resilient to failures. However, the benefits of adopting this approach do not come by themselves: they involve mastering new challenges such as managing network communication, security, an extensive infrastructure and monitoring. For this reason it is not worth entering the world of microservices without a solid plan and a properly trained team. Setting service boundaries correctly is very important so that the application does not become excessively fragmented, which in the longer run could worsen efficiency and increase maintenance costs. Even so, when microservices are rolled out sensibly, they become a powerful tool in the hands of developers and the business. They make it easier to react quickly to changing market conditions, they allow selected functions to be scaled as needed and they give individual teams more autonomy. All of this together means that microservice architecture is gaining more and more popularity among companies that bet on innovative solutions and dynamic growth.
