[box]Software companies large and small are embracing microservices as a superior approach to application development and management, compared to the earlier monolithic model that combines a software application with the associated user interface and underlying database into a single unit on a single server platform. With microservices, a complex application is broken up into a series of smaller, more specialized services, each with its own database and its own business logic. Microservices then communicate with each other across common interfaces (like APIs) and REST interfaces (like HTTP). Using microservices, development teams can focus on updating specific areas of an application without impacting it as a whole, resulting in faster development, testing, and deployment.[/box]
The monolithic architecture is considered to be a traditional way of building applications. A monolithic application is built as a single and indivisible unit. Usually, such a solution comprises a client-side user interface, a server side-application, and a database. It is unified and all the functions are managed and served in one place.
Normally, monolithic applications have one large code base and lack modularity. If developers want to update or change something, they access the same code base. So, they make changes in the whole stack at once.
Strengths of the Monolithic Architecture
- Less cross-cutting concerns. Cross-cutting concerns are the concerns that affect the whole application such as logging, handling, caching, and performance monitoring. In a monolithic application, this area of functionality concerns only one application so it is easier to handle it.
- Easier debugging and testing. In contrast to the microservices architecture, monolithic applications are much easier to debug and test. Since a monolithic app is a single indivisible unit, you can run end-to-end testing much faster.
- Simple to deploy. Another advantage associated with the simplicity of monolithic apps is easier deployment. When it comes to monolithic applications, you do not have to handle many deployments – just one file or directory.
- Simple to develop. As long as the monolithic approach is a standard way of building applications, any engineering team has the right knowledge and capabilities to develop a monolithic application.
Weaknesses of the Monolithic Architecture
- Understanding. When a monolithic application scales up, it becomes too complicated to understand. Also, a complex system of code within one application is hard to manage.
- Making changes. It is harder to implement changes in such a large and complex application with highly tight coupling. Any code change affects the whole system so it has to be thoroughly coordinated. This makes the overall development process much longer.
- Scalability. You cannot scale components independently, only the whole application.
- New technology barriers. It is extremely problematic to apply a new technology in a monolithic application because then the entire application has to be rewritten.
While a monolithic application is a single unified unit, a microservices architecture breaks it down into a collection of smaller independent units. These units carry out every application process as a separate service. So all the services have their own logic and the database as well as perform the specific functions.
Within a microservices architecture, the entire functionality is split up into independently deployable modules which communicate with each other through defined methods called APIs (Application Programming Interfaces). Each service covers its own scope and can be updated, deployed, and scaled independently.
Strengths of the Microservice Architecture
- Independent components. Firstly, all the services can be deployed and updated independently, which gives more flexibility. Secondly, a bug in one microservice has an impact only on a particular service and does not influence the entire application. Also, it is much easier to add new features to a microservice application than a monolithic one.
- Easier understanding. Split up into smaller and simpler components, a microservice application is easier to understand and manage. You just concentrate on a specific service that is related to a business goal you have.
- Better scalability. Another advantage of the microservices approach is that each element can be scaled independently. So the entire process is more cost- and time-effective than with monoliths when the whole application has to be scaled even if there is no need in it. In addition, every monolith has limits in terms of scalability, so the more users you acquire, the more problems you have with your monolith. Therefore, many companies, end up rebuilding their monolithic architectures.
- Flexibility in choosing the technology. The engineering teams are not limited by the technology chosen from the start. They are free to apply various technologies and frameworks for each microservice.
- The higher level of agility. Any fault in a microservices application affects only a particular service and not the whole solution. So all the changes and experiments are implemented with lower risks and fewer errors.
Weaknesses of the Microservice Architecture
- Extra complexity. Since a microservices architecture is a distributed system, you have to choose and set up the connections between all the modules and databases. Also, as long as such an application includes independent services, all of them have to be deployed independently.
- System distribution. A microservices architecture is a complex system of multiple modules and databases so all the connections have to be handled carefully.
- Cross-cutting concerns. When creating a microservices application, you will have to deal with a number of cross-cutting concerns. They include externalized configuration, logging, metrics, health checks, and others.
- Testing. A multitude of independently deployable components makes testing a microservices-based solution much harder.
[box]Microservices and containerization work well when used together. Containers provide a lightweight encapsulation of any application, whether it is a traditional monolith or a modular microservice. A microservice, developed within a container, then gains all of the inherent benefits of containerization—portability in terms of the development process and vendor compatibility (no vendor lock-in), as well as developer agility, fault isolation, server efficiencies, automation of installation, scaling and management, and layers of security, among others.[/box]