GraphQL

GraphQL is a query language for your API, and a server-side runtime for executing queries by using a type system you define for your data. GraphQL isn't tied to any specific database or storage engine and is instead backed by your existing code and data.

The Core Difference Between REST APIs and GraphQL

A REST API is an architectural concept for network-based software. GraphQL, on the other hand, is a query language, a specification, and a set of tools that operates over a single endpoint using HTTP. In addition, over the last few years, REST has been used to make new APIs, while the focus of GraphQL has been to optimize for performance and flexibility.

Queries and Mutations

Directives

We discussed above how variables enable us to avoid doing manual string interpolation to construct dynamic queries. Passing variables in arguments solves a pretty big class of these problems, but we might also need a way to dynamically change the structure and shape of our queries using variables. For example, we can imagine a UI component that has a summarized and detailed view, where one includes more fields than the other.

Mutations

Most discussions of GraphQL focus on data fetching, but any complete data platform needs a way to modify server-side data as well.

In REST, any request might end up causing some side-effects on the server, but by convention it's suggested that one doesn't use GET requests to modify data. GraphQL is similar - technically any query could be implemented to cause a data write. However, it's useful to establish a convention that any operations that cause writes should be sent explicitly via a mutation.