What are advantages and disadvantages of microservices and monolithic architecture?
When to chose microservice architecture or monolithic architecture?
While I'm relatively new to the microservices world, I'll try to answer your question as complete as possible.
When you use the microservices architecture, you will have increased decoupling and separation of concerns. Since you are litteraly splitting up your application.
This results into that your codebase will be easier to manage (each application is independent of the other applications to stay up and running). Therefore, if you do this right, it will be easier in the future to add new features to your application. Whereas with a monolithic architecture, it might become a very hard thing to do if your application is big (and you can assume at some point in time it will be).
Also deploying the application is easier, since you are building the independent microservices separately and deploying them on separate servers. This means that you can build and deploy services whenever you like without having to rebuild the rest of your application.
Since the different services are small and deployed separately, it's obvious easier to scale them, with the advantage that you can scale specific services of your application (with a monolithic you scale the complete "thing", even if it's just a specific part within the application that is getting an excessive load).
However, for applications that are not intended to become too big to manage in the future. It is better to keep it at the monolithic architecture. Since the microservices architecture has some serious difficulties involved. I stated that it is easier to deploy microservices, but this is only true in comparison with big monoliths. Using microservices you have the added complexity of distributing the services to different servers at different locations and you need to find a way to manage all of that. Building microservices will help you in the long-run if your application gets big, but for smaller applications, it is just easier to stay monolithic.