The Five API Styles: Understanding RPC, Resource, Hypermedia, Query, and Event-Based APIs

APIs are languages, and languages can be designed very differently. In this video, we discuss "language families", i.e. different general approaches that API design can take. We discuss the five API styles, which are the Tunnel Style, the Resource Style, the Hypermedia Style, the Query Style, and the Event-based Style.
We also look at popular examples of how APIs using these styles are being implemented and described today. Technologies such as REST, OpenAPI, HTTP, gRPC, GraphQL, AsyncAPI, and Kafka are all examples of specific styles, and we look at them as examples of these styles.
This video helps you to better understand API styles and to take a step back before discussing specific technologies. API styles can be regarded as "technology families", for example both SOAP and gRPC are examples for the Tunnel Style, but they were created at different times and with different design details.
Regardless of the details: API design is important, and too often default decisions are made instead of thinking through the problem at hand and the resulting design constraints. This video helps you to understand the five API styles so that you can design better APIs.
This video may be helpful for anybody interesting in systems design and engineering, for example when researching and preparing for a systems design interview. Understanding API styles and how they relate to API technologies is crucial in today's API-based landscapes.


00:00 Intro
01:02 APIs are Languages
01:40 Design Constraints for APIs
02:56 Tunnel Style
04:01 Resource Style
05:20 Hypermedia Style
07:08 Query Style
08:42 Event-Based Style
10:22 Summary
12:05 Outro