How to move from a monolithic architecture to microservices?

Cloud services development and the need for rapid updates in the changing business world result in the mass transition from a monolithic to a microservice architecture. Learn here what a microservice architecture is and whether it’s worth moving from a monolithic one. Stay tuned!

What is Monolithic Architecture?

The concept of monolithic software suggests that the various app components are combined into a single program on a single platform. Typically, a monolithic application consists of a database, a client user interface, and a server application.

What is Microservices Architecture?

The microservices architecture is an approach to software that builds a system as a set of independent and loosely coupled services.

In a microservice architecture, loosely coupled services interact with each other to perform tasks related to their business capabilities. You can guess that microservices get their name because the services are smaller than in a monolithic environment. But first and foremost, micro isn’t about size, but the opportunity to develop business faster and greater. 

Difference between Microservices & Monolithic services 

The battle “monolithic vs microservices” is unceasing. In general, microservice and monolithic architecture differ in their approach to the application. Let's analyze the main differences between microservices and monolithic services according to the key criteria:

Structure. A microservice application consists of many small independent and loosely coupled services, while in a monolith, all its components are closely interconnected and work as a single service.

Scale and modernization. If any process in an application with a monolithic architecture becomes more in demand, it is necessary to scale the entire application. Failure in any one process can compromise the whole system. Finally, this complexity limits the possibilities for modernization and makes it challenging to introduce new ideas.

Consistency. With a monolithic architecture, it is easier to maintain code consistency and handle errors. But microservices can be fully managed by different teams in compliance with different standards.

Modularity. A monolithic architecture makes it easier to work in situations where several modules need to interact with each other or when you want to move classes from one module to another. In the case of microservices, it is imperative to define the boundaries of modules clearly.

Microservices: pros and cons 

Pros: 

• ​​Microservices are handy in modular management due to the isolated development of functionality and rigid boundaries between individual services.
• Microservices provide for independent deployment.
• A well-designed microservice architecture has a faster release pace due to the independent nature of each unit. 
• Microservices are smaller and therefore easier to understand and test. Smaller sizes help when it comes to compiling time, launch time, and the time for running tests. This improves the developer's productivity as they spend less time waiting at each stage of development.
• Microservices architecture is polyglot. You can use different programming languages and migrate from one language to another.
• Microservices are not tied to the technology used in other services. It's easy to rewrite old services to use new technologies quickly.

Cons:

• A distributed system with many independent elements is more organizationally and architecturally complex. Managing development and deployment teams becomes more complicated, requiring Agile and DevOps methodologies.
• Increased network delays and potential failures due to distributed access to services. Asynchronous and reducing the number of calls can help to overcome these challenges.
• Due to decentralization and modularity, data inconsistency can occur, leading to failures and unavailability of the whole application. In this case, it is worth looking for compromises between the availability of services and consistency.

The most successful cases of microservices

In 2022, the successful implementation of microservices is no longer an innovation but a must-have of the times. Among successful microservices implementers are Amazon, Google, Netflix, and Twitter.

Amazon’s “service-oriented architecture” was the predecessor of modern microservices. The company developed some solutions to maintain microservices architectures, such as Amazon AWS (Amazon Web Services) and Apollo. Currently, these solutions are sold globally.

Netflix is one of the first eminent corporations that migrated from a monolithic to cloud-based microservices architecture. Currently, this company has over a thousand microservices providing management and support to the separate parts of the streaming platform.

Google infrastructure consists of integrated systems having many features of modern microservices. The same relates to Twitter. The company developed a mechanism of re-architecture from a Ruby monolith. As a result, many HTTP microservices currently implement the public Twitter API v1. 1 endpoints.

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How are software development processes performed on the project with microservices? 

With the ever-increasing demand for large-scale applications, microservices fill the need for a more focused approach to software development that drives business growth.

The most crucial point in software development processes is always to remember that you work with microservices. It means that when a developer changes something, it can affect not only the part of the system you’re working on but also some microservices, clients, etc. It can be like a chain.

These complexities are expected since, with microservices, your system becomes more complex. You have more members inside it and relations between them.

But supporting and improving a microservice system is more straightforward than monolithic, even if your system is complex. Each part of it becomes simpler and more understandable. Sometimes processes can seem harder than with one monolith, but it’s worth it because if you separate the system right, it will be more productive and stable.

How to move from a monolithic architecture to microservices?

If you decide to separate your application into several microservices, you should think about several things:

1. Prepare a plan for your future parts

You must understand which part of the functionality microservice will be responsible for. These parts can and will be different on different projects. But there are some typical, i.e., Auth service, File service, Payment service, Notification service.

We don’t recommend creating all microservices at the same time. Start from one microservice. This practical approach allows you to find all pitfalls and dive into the moving process.

It is good to start with the most isolated or essential part, which you need to isolate to make it better and more efficient.

2. Decide on the data and database structure

Decide which data will be stored in the microservice DB (database), prepare the DB structure, and find a way to migrate the data from the main service to the microservice without losing it. After successful migration, the data from the main service will be deleted.

3. Choose a communication method between a microservice and other parts of the system

There are two of them, synchronous (HTTP) and asynchronous (Message). They can be combined in some cases.

Message communication is good when the main service doesn’t need to get any data from the microservice. Its job is only to push a message to Message Broker (i.e., RabbitMQ, ActiveMQ). Then, the microservice must take this message from Message Broker and handle it. Generally, a message is a JSON object containing all information needed for the correct execution of a task. This method can be used in the Notification microservice, which is responsible for sending emails, push notifications, SMS, etc.

The HTTP communication is used when your main service or client needs to fetch some data and get some response on a request. The most popular approach here is REST API. So, the main service or client creates and sends requests to the microservice and receives responses. What can be simpler? 

It sounds easier than Message communication, but microservice should always be on with this communication method. In the case of Message, it will be just a delay in task execution, but data will not get lost. Also, HTTP communication can be a little slower.

In both cases, you must create a contract that allows you to send all data between parts of the system correctly. In the case of Message, the contract is a structure of JSON objects. Therefore, it’s a good practice to send only needed information and have strict types of fields.

If you have chosen HTTP communication, you must prepare API documentation of future endpoints with a description of the request body, response, possible errors, headers, etc.

4. Pay attention to the deployment process

It would help if you prepared a plan of deployment in advance. For example, think about the order of services deployment, on which step data will be migrated, checking of work, etc. Discussion and consideration of these points can decrease time and problems of development. 

To reduce the cost of the transition from monolith to microservices and make it as effective as possible, we recommend working with professionals with sufficient experience in this field.

Conclusion

The solution "monolithic vs microservices" depends on your company's needs, possibilities, and organizational structure. We at Axon recommend not hesitating if you have enough resources to move to microservices architecture. With a microservice architecture, developers can create flexible, function-oriented services. The high rate of change and increased complexity will be decisive factors that will drive your choice!