Monolithic to Microservices: When, Why, and How to Take Transition

You must think wisely before you make decisions on migrating a monolithic application to a microservices equivalent. Overlooking the right time to take the migration step can push you far behind the competition.

In recent years, the shift from monolithic to microservices architecture has become a popular trend in software development. As organizations look to improve the scalability and flexibility of their applications, the move from a monolithic to a microservices architecture has become an increasingly popular option. But what exactly is this transition, and why might it be the right choice for your organization?

This article explores the differences between monolithic, N-tier, and microservices architectures. It also discusses when and how to migrate to a microservices architecture.

Let’s dive in! 😀

What is the Monolithic Architecture?

Monolithic architecture is a software design pattern in which an entire application is built as a single, self-contained unit. In a monolithic architecture, all of the application’s components, including the user interface, business logic, and data storage, are combined into a single codebase.

Pros 👍

• Simplicity: A monolithic architecture is easy to understand and work with.
• Easy deployment: A monolithic application is a single unit, making it easy to deploy.
• Improved performance: Communication between components in a monolithic application is faster, leading to improved performance.
• Cost savings: A monolithic architecture may be less expensive to develop than other architectures.
• Familiarity: Many developers are familiar with monolithic architectures and may prefer this approach.

Cons 👎

• Flexibility issues: Changing one component can affect the entire system in a monolithic architecture.
• Scaling difficulties: Scaling a monolithic application requires scaling the entire system.
• Higher maintenance costs: Maintaining a monolithic architecture can be costly and time-consuming as the application grows and becomes more complex.
• Limited code reuse: It may not be easy to reuse code across different application parts in a monolithic architecture.

What is the Multi-tier Architecture?

In multi-tier architecture, we divide a system into several layers or tiers. These layers work together to perform a specific function. First, each layer is responsible for one particular aspect of the system. Then, they communicate with each other to accomplish a task.

Overall, this architecture works on separating the concerns and uses layers for each specific task. For example, the following image shows a 3-tier architecture for a typical MVC application. The model layer handles the data sources, and the View serves as the presentation layer. The controller acts as a handler between the model and the view layers.

Pros 👍

• Improved security: Different application tiers make it harder for attackers to access sensitive data or functionality.
• Better scalability: The tiers can be scaled independently, making it easier to handle increases in usage or load on the system.
• Enhanced maintainability: The separation of concerns in a multi-tier architecture simplifies maintenance and updates of different application parts.
• Enhanced flexibility: The modular architecture allows greater flexibility in adding or changing functionalities. Additionally, integrations with other systems are also easier.
• Enhanced Code Reuse: The Layered design supports modularity. You can use the same business logic layer with different presentation layers.

Cons 👎

• Increased complexity: Using multiple tiers can add complexity to the system, making it harder to understand and maintain.
• Increased development time: Building a multi-tier architecture can take longer than a single-tier architecture due to the additional layers and communication between them.
• Increased deployment and configuration efforts: Deploying and configuring a multi-tier system can be more time-consuming and complex than a single-tier system.
• Increased hardware and infrastructure requirements: A multi-tier architecture may require more hardware and infrastructure resources to run properly.
• Increased testing efforts: Testing a multi-tier system can be more complex and time-consuming due to the additional layers and communication between them.

What is Microservices Architecture?

Microservices architecture breaks down an application into small, independent services that communicate through APIs.

This approach allows for greater flexibility and scalability, as each service can be developed and deployed independently. Additionally, scaling up or down as per demand becomes easier. Therefore, microservices architecture is particularly well-suited for cloud-based environments, where resources can be quickly allocated and deallocated as needed.

Pros 👍

• Scalability: Microservices can scale independently, which allows you to scale specific parts of your application as needed.
• Resilience: If one microservice fails, the other services can continue functioning. This improves the overall resilience of the application.
• Modularity: You can develop, test, and deploy each microservice independently. Therefore, modifying or updating the individual services becomes more manageable.
• Flexibility: With microservices, you have the flexibility to choose different technologies for different services. Thereby, it allows you to use the best tools for each job.
• Ease of deployment: You can deploy microservices independently, which makes it easier to deploy new versions of the application.

Cons 👎

• Increased complexity: Managing multiple independent services can be more complex.
• Higher resource requirements: Running many services can require more resources and infrastructure.
• Increased communication overhead: Communicating among the services requires APIs.
• Increased testing and deployment complexity: Testing and deploying many services can be complex.

Monolithic vs. Multi-tier vs. Microservices

The following table summarizes all the major differences: –

Monolithic to Microservices: What is the Right Time to Take a Transition

There is no one-size-fits-all answer to this question, as deciding a migration from a monolithic to a microservices architecture will depend on your application’s specific needs and goals. Here are a few factors to consider when deciding whether to make the transition:

• Size and complexity of the application: A microservices architecture may make it easier to develop and maintain if your application is large and complex, with many interconnected components. However, a monolithic architecture may be sufficient if your application is relatively small and simple.
• Required level of scalability: If your application needs to scale quickly and easily to meet changing demands, a microservices architecture may be a better choice. As microservices can scale independently, you can scale specific parts of your application per your need.
• Required level of flexibility: If you need to be able to modify or update individual components of your application without affecting the entire application, a microservices architecture may be a better choice. This is because each microservice can be developed, tested, and deployed independently.
• Resources available for development and maintenance: If you have a large team with the skills and resources to develop and maintain a microservices architecture, it may be a good choice for your application. However, a monolithic architecture may be more manageable if your team is small or lacks the necessary skills.

Monolithic to Microservices: The Successful Journeys

Ultimately, the decision to transition from a monolithic to a microservices architecture will depend on your application’s specific needs and goals. It is essential to carefully evaluate the pros and cons of each architectural style and choose the one that best meets the needs of your application.

You might expect practical case studies to evaluate how large companies make migration decisions. Let’s discuss the case studies of Amazon and Netflix to know how they identified the right time for the migration.

Amazon case study

Amazon is a well-known retail giant that originally used a monolithic architecture for its website. However, as the code base grew and the number of developers working on the platform increased, it became increasingly difficult to untangle dependencies and make changes or updates to the platform. This led to development delays and coding challenges and also made it difficult for the company to scale the platform to meet the needs of its rapidly growing customer base.

To address these challenges, Amazon broke its monolithic applications into smaller, independently running, service-specific applications. This involved analyzing the source code and pulling out units of code that served a single functional purpose, wrapping them in a web service interface, and assigning ownership of each service to a team of developers.

The microservices approach enabled Amazon to make changes and updates to its platform easily. Additionally, it allowed for the on-demand scaling of specific components. Despite the challenges involved in the transition, the benefits of the microservices architecture have been significant. Amazon’s e-commerce platform now handles over 2.5 billion product searches daily and includes millions of products from hundreds of thousands of sellers.

Netflix case study

Netflix is a very popular and known company nowadays. It is available in 190 countries and has over 223 million paid users as of 2022.

In 2008, Netflix faced a major database corruption, and the issue persisted for 3 long days. This was the point where the company realized issues of single-point failures of monolithic design. So, Netflix gradually migrated from monolithic to cloud microservices architecture using the Amazon web services.

Netflix took years to migrate its customer-facing and non-customer-facing apps. Yet, the benefits are enormous. The company’s monthly watch hours increased by 1000 times sharply between 2008 and 2015 ~ resulting in high revenues and profits.

How to Migrate your Application from Monolithic to Microservices Architecture Manually

There are multiple steps you can follow for the migration (manual) of your application from a monolithic to a microservices architecture:

1. Identify the business capabilities of your application: The first step in the migration process is to identify the different business capabilities of your application. This step involves analyzing whether these capabilities can be implemented as independent microservices.
2. Split the application into microservices: Once you have identified the business capabilities of your application, you can begin splitting the application into microservices. This may involve refactoring the code base to separate the different capabilities into independent services.
3. Design the interfaces between the microservices: Each microservice should communicate with the other microservices through well-defined interfaces or APIs. It is important to design these interfaces carefully to ensure they are easy to use and maintain.
4. Implement the microservices: Once you have split the application into microservices and designed the interfaces between them, you can begin implementing them. This may involve building new services or refactoring existing code to fit the microservices architecture.
5. Test and deploy the microservices: Once you have implemented the microservices, it is essential to test them thoroughly to ensure that they are functioning as expected. You can then deploy the microservices to production, either individually or as a group.
6. Migrate the data: If your application uses a database or other data storage system, you must migrate the data from the monolithic application to the microservices. Additionally, you may need to design new data models or refactor the existing data to fit the microservices architecture.

Overall, migrating from a monolithic to a microservices architecture can be complex and time-consuming. It is essential to carefully plan and execute the migration to ensure success.

Handy tools for monolithic to microservices migration

There are several tools that can help with the process of decomposing a monolithic application into microservices. For example, IBM’s Mono2Micro, Decomposition Tool, and Decomposer are the most popular tools that help in the decomposition process.

These tools provide a set of automated or semi-automated mechanisms to identify microservices and refactor the code. Additionally, they help set up and manage the infrastructure needed to host the microservices.

Auto-decomposition for Monolithic to Microservices Migration: A Futuristic Trend

The latest boom in artificial intelligence and machine learning has revolutionized traditional approaches to performing our tasks. Wouldn’t it be wonderful if machines could do the complex monolithic to microservices decomposition tasks?

Though it may seem easy to employ AI to help decompose a monolithic application into microservices. Still, it is a path full of challenges. That’s why you find only a few complete studies on this task.

Abdullah et. al. proposed an unsupervised learning approach for web application auto-decomposition into microservices. The following conceptual diagram shows the overall working of the auto-decomposition process.

The auto-decomposition process follows three simple steps.

Step 01: Access URI access logs

Every webpage on a website has a unique uniform resource identifier (URI). Luckily, web servers hosting such applications maintain access logs (e.g., response time and document size) to these URIs. The first step is to gather these access logs.

Step 02: Apply clustering ML algorithm

A clustering algorithm is an unsupervised machine learning method that, given a set of data points, creates K clusters having data points of similar nature. This clustering algorithm, when fed with the historical access logs data, creates clusters of URIs having similar access time and response document size.

Step 03: Clusters to microservices deployment

You can make a microservice for each cluster of URIs. Then, you can deploy these microservices to any cloud infrastructure.

Note: This auto-decomposition technique is specific to monolithic web applications and is only presented to give you an idea about the latest trends in the era.

Best Practices to Migrate from Monolithic to Microservices Architecture

Here are some best practices to follow when migrating from a monolithic to a microservices architecture:

• Start small: It is often best to start by migrating a small, self-contained part of the application to a microservices architecture. This allows you to learn from the process and make any necessary adjustments before tackling the larger parts of the application.
• Identify the right microservices: Carefully identify the business capabilities of your application. It also requires determining whether these capabilities are implementable as independent microservices.
• Design clear interfaces: Ensure that the interfaces between the microservices are well-defined and easy to use. This will make it easier to develop and maintain the microservices.
• Use containers: Containers can make deploying and managing microservices easier, allowing you to package the microservice and its dependencies together in a single, self-contained unit.
• Use a microservices-friendly infrastructure: To support a microservices architecture, you will need an infrastructure that can handle the increased complexity and traffic generated by the microservices. This may involve using technologies such as service meshes, API gateways, and distributed tracing.
• Test thoroughly: Thoroughly test the microservices to ensure that they are functioning as expected and that the interfaces between them are working correctly.
• Monitor and manage the microservices: It is important to monitor their performance and health and take appropriate action if issues arise. This may involve using tools such as log analysis, performance monitoring, and error tracking.

In short, careful planning and execution is a key to a successful migration. By following these best practices, you can ensure that the migration goes smoothly, fulfilling the very purpose.

Conclusion

Microservices architecture is the most flexible and scalable architecture for the modern cloud computing era. It allows you to scale specific parts of the application as needed and modify or update individual services without affecting the entire application. However, it can also be more complex to develop and maintain.

Ultimately, the choice of architecture style will depend on the specific needs and goals of your application. Factors to consider include the size and complexity of the application, the required level of scalability and flexibility, and the resources available for development and maintenance.