Transition from a monolith to microservices in 8 steps

What exactly are microservices?

A microservice is a self-contained software component that implements a single business capability.

It has its own database, exposes a dedicated API and can be deployed independently , which reduces coupling with the rest of the information system and allows for faster updates.

The concept is not entirely new. It is based on historical principles of software engineering:

• Each software component performs a single function and does it correctly.
• Each service is designed to be reusable and compostable.
• The tests are quick and can be automated.

These principles extend modularization approaches such as object-oriented programming and service-oriented architecture (SOA), but with a much higher level of autonomy for individual services.

Microservices architecture has become established thanks to the convergence of several developments:

• DevOps practices and continuous integration,
• containerization and the cloud,
• automation of continuous deployment and delivery.

This combination now makes it possible to break down a monolithic system into independent components while maintaining a high level of reliability and performance.

Microservices are not a one-size-fits-all solution

Before undertaking the transformation of a monolithic system to a microservices architecture, it is essential to assess the real needs in terms of scalability, update frequency and team organization.

In certain contexts, maintaining a centralized architecture remains the most relevant choice:

• Reduced functional scope : operational complexity (CI/CD, observability, network, security) may outweigh the benefits.
• Stable application over time : in the absence of scaling or continuous delivery challenges, breaking down into individual services provides little value.
• Strong technical or functional coupling : some dependencies are difficult to isolate without significant redesign.
• High transformation cost : migration involves changes in architecture, tools and skills.

Environments handling sensitive data also require specific analysis.

Distribution across multiple services can complicate access and flow management, even if it subsequently allows for finer isolation and more granular security control.

In practice, the adoption of microservices is therefore primarily a decision linked to business challenges, the ability to industrialize deployments, and the maturity of teams on distributed architectures.

Why adopt a microservices architecture?

Transforming a monolithic application into microservices brings tangible benefits in terms of performance, team organization, and scalability. The effort can indeed be worthwhile, particularly with regard to the following concepts:

• Scalability: Decomposing a monolithic service into microservices can improve scalability by allowing independent scaling of different functional areas.
• Flexibility: Microservices can improve flexibility by allowing independent development and deployment of different functional areas, making it easier to modify or extend the application.
• Resilience: Independent management and monitoring of different functional areas can improve application resilience.
• Collaboration: If different teams are working on different parts of the application, microservices can facilitate their independent work and improve collaboration.
• Stack: By using microservices, it is possible to use different technology stacks (programming language, database for each application domain, which ensures the use of the most suitable technology for each domain). This can offer many advantages, such as improved performance, maintainability, and scalability.
• Security: Furthermore, decomposing a monolithic service into microservices can improve security by enabling more granular access control and the isolation of sensitive data. With microservices, it is easier to implement security mechanisms such as authentication and authorization at the service level, allowing for finer-grained access control. Moreover, by isolating sensitive data in separate services, it is possible to limit the exposure of this data and reduce the risk of security compromises.

8 steps to transition to microservices:

There is no single method for transforming a monolithic system into a microservices architecture.

On the other hand, a structured approach makes it possible to reduce risks and gradually industrialize the transformation.

Here are the 8 recommended steps:

1. Defining the scope: first, identify the distinct functional areas of a monolithic system, such as user management, security management, identity management… For this, the “DDD” (domain driven design) method can be useful.
2. Decompose the application: divide a monolithic system into smaller, independent services that can be developed, deployed, and scaled autonomously.
3. Define the API contract: Define the API contract for each service, which includes the data structures and methods that can be called. This ensures that services can communicate with each other reliably and consistently. Furthermore, common code should be separated into modules that can be shared between multiple services.
4. Continuous integration and delivery: Implementing a robust continuous integration and delivery (CI/CD) pipeline automates the deployment process and ensures that new services are deployed quickly and reliably.
5. Code refactoring: Revise the code of a monolithic system to align it with the new architecture. This may involve transferring code from the monolithic software to the new services and modifying the code to adhere to the new API contract. It may also be necessary to modify the code to use the new technologies required for microservices.
6. Testing: Once the microservices have been developed and the code has been refactored, test the system to detect errors and performance issues.
7. Monitoring: Microservices require regular monitoring to ensure they are functioning correctly and to detect problems as soon as they occur.
8. Optimize: Finally, optimize microservices to make them more efficient and perform better when needed. Microservices offer the flexibility to update and improve individual services without affecting the entire application.

Best practices for successful microservices architecture

In a distributed architecture, a request may traverse several services before producing a response.

Therefore, it is essential to implement correlated logging : each call must transmit a unique identifier. This allows you to track the path of a request, debug quickly, and improve overall observability.

Distributed transaction management is another critical point. An operation that was once handled by a single application block must now be coordinated across multiple services. Anticipating this need from the design stage avoids costly redesigns and ensures data consistency.

A phased migration is the safest strategy. Starting by isolating an initial, low-risk feature allows you to validate the continuous integration and continuous delivery (CI/CD) pipeline, independent service deployment, and team organization. Traffic routing can then be progressively extended to new services, thus mitigating risks.

Finally, the technology choice must be tailored to the team's skills. While each department may use a different language, it is essential to guarantee maintainability , long-term support capabilities, and rapid adoption by the teams. The goal is to balance innovation with operational stability.

I want to get started on that, actually!

Our message is clear: taking the time and careful thought before embarking on microservices can prevent long-term problems. Good planning and thoughtful design are essential to ensure a successful migration to a microservices-based architecture.

If your team lacks the necessary expertise in distributed systems, microservices, and containerization, don't worry! Ours does. Call on our experts!