Microservice applications versus monoliths

The benefits of microservice architectures can be better understood by comparing them with monolithic architectures.

The benefits of microservices over monoliths are phenomenal when they are designed and deployed correctly.

It is not as simple as splitting a monolithic application based on structure, component, or functionality and then deploying them as individual services. This will not work out. Converting a monolithic application or even a monolithic design into microservices needs a clear vision of the product. It includes knowledge of what part of the project will change and what part will be consistent. We must have low-level details, such as which entities we should group together and those that can be separated. 

This clearly illustrates the need for an ever-evolving model. It is much easier to split the technologies used in the application, but not the interdependent models or the business logic of the application. So it is essential to place the project's primary focus on core domain and its logic.

Microservices should be independent. They will fail when a component is tightly coupled with another. The trickiest part is identifying and segregating the components.

When we have done that, it offers the following benefits over monolithic applications.

The monolithic code is a single unit. Thus, all parts of the application share the same memory. For a bigger system, we need to have a bigger infrastructure. When the application grows, we need to scale the infrastructure as needed. The scaling of an already bigger infrastructure is always a difficult and costlier task for operations. 

Even though they have all the necessary code to handle anything in the product at a single place (no need to worry about latency or availability), it is difficult to handle the resources that it consumes to run and it is definitely not scalable. If any one part of the application fails, then the whole product will be impacted. When any one thread or query of the product clings on to the memory, then the impact will be seen by millions of our customers.

Microservices, on the other hand, require less memory to run since we are splitting the application into smaller components, which in turn reduces the infrastructure's cost. For example, it is cheaper to run 10 2GB instances (costs ~$170 per month on AWS) than running a single 16 GB instance (costs ~$570 per month on AWS). Each component runs in its own environment, which makes microservices much more developer-friendly and cloud-native. Similarly, microservices also increase the throughput across services. A memory intensive operation on one service will not affect any other service.

Monolithic architecture, over a period of time, will remove the agility of a team, which will delay the application rollout. This means people will tend to invest more time to find a workaround to fix a problem when a new feature is added, or something in the existing feature breaks. The monolithic architecture will bring a greater amount of inefficiency that in turn increases the technical debt.

Microservices, on the other hand, reduce the technical debt in terms of architecture since everything is reduced to individual components. Teams tend to be more agile and they will find handling changes easier.

The less code there is, the fewer bugs there are, meaning less pain and a shorter time to fix.

Monolithic applications are more time consuming to work with. Imagine there is a big monolithic application and you have to reverse an if condition in your service layer. After changing the code, it has to be built, which usually takes a few minutes, and then you must test the entire application, which will reduce the team's performance.

You can reboot or reload an application in seconds for a microservice architecture. When you have to reverse an if condition, you need not wait for minutes to build and deploy the application to test, you can do it in seconds. This will decrease the time it takes to do mundane tasks.

Faster iterations/releases and decreased downtime are the key things to increase user engagement and user retention, which in turn results in better revenue.

A human mind (unless you are superhuman) can handle only a limited amount of information. So cognitively, microservices help people to reduce the clutter and focus on the functionality. This enables better productivity and faster rollouts.

Embracing microservices will: