Microservices is an application development model that is increasingly replacing the traditional monolithic architecture. It gives systems more flexibility and makes them easier to scale. It also allows to reduce development costs. What are the two approaches, what are their advantages and disadvantages, and how do you free yourself from the inconvenience of monolithic architecture?

Imagine two Lego castles. One has blocks glued together with super glue, while the other does not. Now a million-dollar question: which castle will be easier to rebuild? This is probably not the most brilliant or accurate analogy, but it neatly outlines the key differences between monolithic and microservices architectures. To put it simply, software designed according to the former model is more difficult to modify and scale than software developed with a microservices approach.

Microservices vs monolithic architecture

Monolithic architecture is the traditional model. It consists in placing all software functions in a single code base and implementing them as a single file. A monolithic system is thus supported by a single application, which is an outcome of the painstaking work of many developers working together.

This is the way software has been developed for many years. Monolithic applications are still widespread. Both as legacy systems – existing implementations, developed according to the classic standard – and new projects, built from scratch.

However, for some time another approach has been gaining popularity – microservices. It has many advantages over the monolithic model, although it is considered more complex and more difficult to implement, at least at the initial stage of development. However, at an advanced stage of application development it seems inevitable, both because of the stability of the system and the costs of maintaining and scaling it.

Inflexible and unpredictable. Disadvantages of monolithic applications

There are quite a few reasons to replace a monolithic application with microservices. The key issue is the flexibility of the latter solution and the "rigidity" of the former. The drawbacks of monolithicity can manifest themselves in a variety of ways. The main burdens associated with this architecture are:

• the components of the application are tightly coupled, so small changes can have an impact on the overall code,
• as a result, individual errors can disrupt the entire system,
• and making even slight modifications requires the entire application to be reimplemented,
• a large monolithic application is difficult to understand and "grasp", which slows down the implementation of changes and increases the risk of mistakes,
• the effects of change are often hard to predict, which necessitates longer and more thorough testing,
• monolithic applications are more difficult to scale, especially when their individual modules have conflicting resource requirements,
• it is not possible to scale individual components, you need to scale the whole application,
• the complexity of a monolithic application makes it increasingly difficult to manage the system as the code base grows,
• for the same reason, it is more difficult to bring new developers on board to work on monolith, which is especially problematic in light of the fact that developers often switch companies and projects.

Scalability and ease of modification. How do microservices work and what problems do they solve?

Of course, this is only a generalized list of problems that monolithic applications can generate. The shortcomings of this architecture can "materialize" in countless ways. On the other hand, microservices are free from most of the weaknesses characteristic of monoliths due to a completely different operation scheme.

The microservices model involves breaking down individual application functions into smaller, interrelated components. In practice, each microservice is a separate application based on business logic separated from external dependencies. Using microservices allows to break down even a very large system into smaller, autonomous parts.

As a result, scaling and modifying the application becomes much simpler, because you do not have to rework it from scratch, it is enough to develop or transform its individual components. In this situation, there is no problem of working out a complex structure and implementing new developers to work on the system. It is enough to define the scope of activity, e.g. adding or modifying a specific function, and then start coding – without fear that in the course of work the whole system will "fall apart" due to an accidental error.

Microservices are the answer to a number of challenges that monolithic applications cannot cope with. They make it easier to develop complex systems and implement new features, reduce working time, and thus the cost of hiring developers. They also reduce the likelihood of errors, which inevitably occur during programming, being encountered and overlooked. It's easier to code and test individual, independent modules than to examine a complex, monolithic system after an update.

Is a monolithic architecture good to start with? Moving to microservices is inevitable

This is not to say that monoliths are doomed to the dustbin of history and should be avoided like a coronavirus. There are several arguments for using this type of application – under certain circumstances. First of all, it is a good solution to start with. It is easier to use than microservices at the application development stage, because it is implemented as a single file, without splitting into modules.

For the same reason, a small monolithic application can also be more efficient than a microservices-based system. It is also easier to bring to market at a lower cost and in a shorter time. However, as a system grows, its monolithic nature becomes a burden and microservice architecture becomes a more desirable solution.

Fortunately, in such a situation, you don’t need to develop a system from scratch. Many companies use a hybrid approach, combining both models: monolithic architecture is used where it is necessary, or at least not burdensome, while microservices are implemented with a view to scaling the system and developing new functions. Of course, such "innovations" should be preceded by a meticulous analysis of needs and possibilities. The point is not to implement microservices just in case or because it is trendy, but for a specific, justified purpose.

How to break a monolithic application into microservices?

An alternative to the hybrid model is to break down a monolithic application into microservices. While this sounds like a risky endeavor, it is actually a relatively easy process to implement with the right tools. One of the solutions available is Amazon Elastic Container Service (Amazon ECS).

It allows you to run a monolithic application in microservices mode after it has been containerized using the Docker platform - software for developing, deploying and running distributed applications. By using Docker, the application and its dependencies are placed in a virtual "container" that can be run on almost any Linux server or service such as ECS.

Containerization of a monolithic application allows individual services to be extracted from the monolith and managed freely – along with all the advantages of this approach, such as:

• risk isolation,
• increasing safety,
• ensuring the possibility of independent scaling of individual services or
• accelerating the pace of application development.

Amazon ECS is a solution that frees you from the burden of legacy systems without having to rebuild them from scratch. If you're looking for a company that can help you address the weaknesses of monolithic applications and exploit the potential that microservices architecture provides, contact us!

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