Introduction
GraphQL, is an open-source data query and manipulation language for APIs, and a runtime for fulfilling queries with existing data.[2] GraphQL was developed internally by Facebook in 2012 before being publicly released in 2015.On 7 November 2018, the GraphQL project was moved from Facebook to the newly-established GraphQL foundation, hosted by the non-profit Linux Foundation.
It provides an efficient, powerful and flexible approach to developing web APIs, and has been compared and contrasted with REST and other web service architectures. It allows clients to define the structure of the data required, and exactly the same structure of the data is returned from the server, therefore preventing excessively large amounts of data from being returned, but this has implications for how effective web caching of query results can be. The flexibility and richness of the query language also adds complexity that may not be worthwhile for simple APIs. It consists of a type system, query language and execution semantics, static validation, and type introspection.
GraphQL supports reading, writing (mutating) and subscribing to changes to data (realtime updates)
Major GraphQL clients include Apollo Client and Relay. GraphQL servers are available for multiple languages, including Haskell, JavaScript, Python, Ruby, Java, C#, Scala, Go, Elixir, Erlang, PHP, R, and Clojure.
On 9 February 2018, the GraphQL Schema Definition Language (SDL) was made part of the specification.