In the 2010s, machines and even smartphones were able to access plenty of CPU resources, and network bandwidths of a few hundred Mbps were everywhere. Developers started to utilize these resources to make application code and system structures as easy as possible, making the software development cycle quicker.

Nowadays, there are sufficient hardware resources available, so it makes sense to use HTTP/SSL as the RPC transport. In addition, from experience, developers choose to make this process easier as follows:

• By making HTTP and SSL/TLS as standard transport
• By using HTTP method for Create/Load/Upload/Delete (CLUD) operation, such as GET, POST, PUT, or DELETE
• By using the URI as the resource identifier, the user with the ID 123, for example, would have the URI of /user/123/
• By using JSON for standard data presentation

These concepts are known as Representational State Transfer (RESTful) design. They have been widely accepted by developers and have become the de facto standard of distributed applications. RESTful applications allow the use of any programming language, as they are HTTP-based. It is possible to have, for example, Java as the RESTful server and Python as the client.

RESTful design brings freedom and opportunities to the developer. It makes it easy to perform code refactoring, to upgrade a library, and even to switch to another programming language. It also encourages the developer to build a distributed modular design made up of multiple RESTful applications, which are called microservices.

If you have multiple RESTful applications, you might be wondering how to manage multiple source codes on VCS and how to deploy multiple RESTful servers. However, CI and CD automation makes it easier to build and deploy multiple RESTful server applications. For this reason, the microservices design is becoming increasingly popular for web application developers.