Until about 2013, companies typically developed enterprise applications as single modules with a large code base, which follows the principles of a monolithic architecture. As software has become more complex and cloud computing has become more popular, this approach has lost its practicality.

With the advent of software-as-a-service products (applications delivered in the cloud), companies have been able to use vendors such as Amazon Web Services to quickly create new servers and add redundancy. As a result, services were not interrupted during upgrades, and a new era of speed and agility began in the world. Users began to expect quick updates and improvements, which prompted companies to change their development processes.

Applications began to break up into small, independent services, or microservices. So, for example, the inbox may not be part of a monolithic e-commerce platform, but a separate microservice that will perform the necessary functions.

At the same time, developers were organized into small, specialized teams that could modify and improve individual services without compromising the performance of the entire application. These teams were often also responsible for exploiting the code they wrote, implementing the DevOps model. In light of these changes, project managers have come up with new methodologies, including Agile, where a project is completed by frequently releasing small releases.

What are microservices?
 
A microservice is a function that is responsible for a single piece of logic (with the exception of domain-specific microservices, which will be discussed below). Several microservices are at the heart of distributed applications such as Jira Software.

There are three types of microservices.

Domain-specific microservices are characterized by loose coupling and similar functionality.
Integration microservices enable communication between unrelated applications.
Elementary operations microservices perform separate functions.
Microservices communicate with each other using application programming interfaces (APIs). Developers responsible for individual services can learn the inner workings of other microservices, which is another advantage over a monolithic architecture.

A microservices-based architecture offers many benefits, but it also increases system complexity.

Key principles of microservices
 
Microservices-based architecture has a number of distinct features. Developers can independently create and deploy services using the most appropriate languages and technologies.

Communication between microservices is API-based, which allows you to access data from multiple sources without the risk of changing it. Individual services scale based on demand, resulting in cost savings and high availability.

These qualities make distributed microservices-based applications flexible and easy to maintain.

Benefits of a microservice architecture
 
Microservices provide a variety of Advantages. They simplify the development and management of projects. Sometimes they can eliminate the need to form separate operations teams, as developers can maintain the microservices they create.

Other benefits of microservices include:
 
Fault tolerance and fault localization
In monolithic architectures, a single bug affects the entire application. But microservices are independent, so the failure of one of them will not affect other parts of the application.
 
Agility
Breaking down applications into smaller parts speeds up development. Teams are able to build, test, and deploy software faster.
 
Technological diversity
Microservices allow developers to choose the right tools and technologies for their work. This improves efficiency and productivity.
 
Improved Maintenance
The ability to test individual components makes it easy to find and fix bugs without having to shut down the entire application.
Problems of microservice architecture
 
Microservices-based architecture has many advantages, but it is not without its challenges.

One of them is that independent services generate their own logs. This is a disadvantage compared to centralized monolith logs, which are a single source of truth for developers and operations teams. Monitoring and managing the infrastructure also becomes more complex because the system is multi-component. Testing and debugging are more difficult because, unlike monoliths, there is no integrated development environment (IDE).

Why do we need a microservices architecture?
 
Large consumer websites often involve hundreds or thousands of microservices. Microservices are particularly useful in the following use cases and industries.

On e-commerce sites like eBay, separate microservices provide shopping carts, mobile apps, and messaging solutions.
Financial institutions such as Bank of America use microservices to communicate with external services, as well as perform functions such as user authorization and transaction display.
On social media platforms such as Instagram and Facebook, microservices are responsible for displaying news feeds, messages, notifications, and networks of friends.

Best practices for managing microservices
 
Over the years, developers have compiled dozens of important guidelines for building microservices. Below are just a few examples.

The Single Responsibility Principle (SRP) stipulates that each module or microservice should have only one function. SRP continuous integration (CI) is a source code management methodology that automates code quality checks before merging it into the project base. This eliminates the need for a separate QA process, so this DevOps best practice helps speed up development. CI precedes continuous delivery (CD), in which automated build tools prepare the software for deployment.
API gateways simplify communication between microservices, help manage authentication and authorization, and improve security.
Asynchronous communication between microservices allows them to maintain autonomy and reduces the number of dependencies that can slow down the application.
Microservices versioning is critical when developers make breaking changes, such as deleting an entire operation. This practice facilitates the transition and minimizes the likelihood of service disruptions.

Microservices Frequently Asked Questions
 
What tools are commonly used in microservices architectures?
Companies often use containerization tools such as Kubernetes and Docker. In addition, API gateways between microservices and their clients are often used. These gateways perform API traffic management functions such as authentication, access control, and load balancing.
What is the difference between a microservice architecture and a monolithic one?
Monoliths are large codebases that function as a single system. When updating or debugging such a system, downtime inevitably occurs. Microservices architectures are distributed applications with small, independent blocks of functions. Developers can update, improve, and debug these modules without shutting down the entire application. This makes it easier to scale and increases the speed of development.
How do microservices affect DevOps?
Those who understand the principles of DevOps know that continuous integration and continuous delivery (CI/CD pipeline in DevOps) are the foundation of the DevOps methodology. The modular nature of microservices fits this approach perfectly. Microservices allow developers to build, test, and deploy small releases quickly and frequently.