Transforming a monolithic architecture to a microservices architecture is a significant task many organizations face as they scale and modernize their applications. In this post, I will walk you through the key considerations and steps involved in this process

What is Monolith Architecture?

A monolithic architecture is a traditional software design pattern where all components are organized into a single codebase and deployed as a single unit. Typically, it will include everything from user interface, business logic, and the database.

What is Microservices Architecture?

Microservices architecture is an approach to software development where an application is built as a collection of small, independent services. Each service runs in its own process, communicates through well-defined APIs, and is responsible for a specific business capability. This architecture allows for greater scalability, flexibility, and easier maintenance of individual components.

When do you want to migrate from monolith architecture to microservices architecture:

• Shorten update cycle: Many times, updating big monolith application is slower than a small service. So if the application is big and needs to change frequently, microservice is a good choice
• Scalability: When different parts of your application have different scaling needs, microservices allow you to scale individual components independently.
• Team organization: For large organizations with multiple teams working on different aspects of the application, microservices can allow for better team productivity.

Migration plan

Without a plan, the migration process can quickly become a disaster. Here are some tips to help you prepare a plan:

• Migrate gradually: Instead of replacing the whole monolith with the new one, we will replace it incrementally.
• Parallel Development: both legacy system and the new system will run and develop in parallel, ensure exisiting logic still work.
• New Module as a Service: For any new module, separate it to a new service.

So, how to migrate from monolith to microservice architecture

1. Mapping the components

How your monolith application organized, how many main modules that you have that independently from each other, carry a specific business logic? We need to identify those modules first.

2. Design communication channels between services.

The next thing is identifying the inter-system communication style between those modules. Was it synchronous or asynchronous operation? Was it 1-1 or 1 to many, identify them.

After that, choose which channel you want to use.

• If it’s 1-1 synchronous, you can use http call.
• If it’s 1-1 asynchronous, you can choose either http call or event bus.
• If it’s 1 to many asynchronous, event bus is the best choice

3. Choose the module that you want to extract to a separate module

The best way is to start with less critical service to minimize the risk and we can learn from the process.

4. Split the code of that module, separate it from the rest of code base.

5. Split the database, form the communication channel between 2 parts to synchronize the data.

Ideally, your microservice doesn’t have shared data across services. But many times, one service will need data from other. Let's say the order service needs user data to process its logic. You have multiple methods to deal with this situation

• Using restAPI: the easiest way is to expose the user data restAPI endpoint and let other services use it.

• Store duplicate data in both services. When performance is important, consider store some user data in order service’s database could be a good choice.

  The challenge is how to synchronize duplicate data between user database and order database. This is called data consistency, and it’s such a big topic in microservice, this post will introduce you many methods to deal with it

6. Moving the new module to a new service, deploying it.

7. Delete the old module in monolith application.

Recap

Transforming a monolithic application to a microservices architecture is a complex process that requires careful planning, gradual implementation, and continuous refinement. I hope my post provide you with some valuable insight, helping you complete this proccess successfully.