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What is an API?

An application programming interface (API) is a piece of software that provides an interface for other software to interact with it.

What is a REST API?

REST or RESTful API design (Representational State Transfer) is an architectural style that uses existing protocols. There are six key constraints for REST API design:

• Using the unified interface (UI)
• Client-server based
• Stateless Operation
• RESTful Resource Caching
• Layered system
• Encoding on demand

What is HTTP REST API?

While REST can be used with almost any protocol, it usually leverages HTTP. So basically an HTTP REST API is an API that uses the HTTP protocol to transfer request/response data between the server and the client while using REST API design principles.

What is a WebSocket REST API?

This is an API that uses the WebSockets protocol (built on top of the HTTP protocol) to transmit request/response data between the server and the client, while using REST API design principles.

Why is this important for responsiveness?

While WebSockets might be overkill when used for just a single request (open web socket -> send request -> get response -> close web socket), they are very fast when we perform multiple requests on a single connection. The whole idea behind WebSockets is to establish a bidirectional communication channel between the client and the server. This means two things:

• This type of connection allows us to receive updates from the server without sending any requests (for example, we can create notifications)
• Because we create a connection only once and use it multiple times (for as many requests as we want), we save a lot of server resources and bandwidth, so we get faster responses.

Performance Testing and Results

The hardware used to perform the tests is an Apple MacBook Pro 16" with an M1 Max processor and 32GB RAM and an iPad mini 4. The server was created inside a VM (2 cores, 4GB ram). NodeJS (v.18.2 .0) was used to create the same “book” mock data for both HTTP REST API and WebSocket REST API. The response length was 358 bytes.

For our testing purpose, we created a simple Flutter application (v3.0.1) to play the role of a testing tool. I chose the Dio package to create HTTP requests and test the HTTP RESP API part and the web_socket_channel package for the WebSocket REST API part. The results of multiple requests are in milliseconds.

Final Thoughts

From the table and graph above, we can see, unsurprisingly, that WebSockets gain more and more ground as the number of requests increases, regardless of whether we are testing on an emulator or a real device.

In my next article, we will explain how to build a simple NodeJS server architecture with API versioning for a WebSocket REST API.