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GraphQL

Table of Contents

What is GraphQL? #

GraphQL is an open-source query language and runtime for APIs (Application Programming Interfaces). It is often used in modern web and mobile application development, where it enables more efficient data fetching, reduces over-fetching and under-fetching of data, and provides a more intuitive and flexible API for clients to consume.

It was initially developed by Facebook and released as open source in 2015. It was then transferred to the newly established GraphQL Foundation in 2018, hosted by the non-profit Linux Foundation. In 2018, the GraphQL Schema Definition Language (SDL) became part of the specification.

What is GraphQL used for? #

GraphQL is used for various purposes in web and mobile application development. Here are some common use cases where GraphQL is particularly beneficial:

  • Efficient data fetching: GraphQL allows clients to precisely request the data they need, eliminating over-fetching or under-fetching of data. This is especially useful in scenarios where bandwidth is limited or when dealing with large and complex data structures.
  • Single API endpoint: Unlike traditional RESTful APIs, which often have multiple endpoints for different resources, GraphQL provides a single endpoint for all data operations. This simplifies the API architecture and reduces the number of network requests required by clients.
  • Mobile applications: GraphQL is well-suited for mobile app development, where network resources and battery life are often limited. By enabling clients to fetch only the required data, GraphQL reduces the payload size and network overhead, resulting in faster and more efficient mobile apps.
  • Microservices architecture: In a microservices environment, where multiple services provide different data sources, GraphQL can act as a gateway that consolidates and abstracts the underlying services. Clients can send a single GraphQL query to retrieve data from multiple services, simplifying the integration process.
  • Rapid development and iteration: The flexibility of GraphQL allows frontend and backend developers to work more independently and repeat processes more quickly. Frontend developers can modify their data requirements without impacting the server, and backend developers can add new features or fields to the schema without breaking existing clients.
  • Real-time applications: GraphQL supports subscriptions, which enable real-time updates. This is particularly useful for applications that require live data updates, such as chat applications, real-time analytics dashboards, or collaborative editing tools.
  • API versioning and evolution: GraphQL’s schema-based approach provides a clear contract between the server and clients. This makes it easier to introduce changes to the API without breaking existing clients. Clients can continue using the older version of the schema until they are ready to adopt the new changes.

GraphQL offers more efficient data fetching, improved developer productivity, and enhanced flexibility in building modern applications that require optimised data retrieval and real-time capabilities.

How does GraphQL work? #

Instead of making multiple requests to different endpoints to retrieve specific data, clients can send a single GraphQL query to the server, specifying exactly what data they need. This query is then processed by the server, which responds with a JSON object that contains only the requested data, eliminating over-fetching or under-fetching of data.

GraphQL has a schema definition language that allows you to define the data structure and types that the API can return. This provides a contract between the server and the client, ensuring that the data is consistent and predictable.

Clients can request multiple resources and nested data structures in a single request, reducing the number of round trips to the server. This minimises network overhead and allows clients to precisely get the data they need.

GraphQL operations are the fundamental units of communication between clients and servers in GraphQL. There are three types of operations:

  1. Query: Used to retrieve data from the server. It resembles a GET request in RESTful APIs.
  2. Mutation: Used to modify data on the server. Mutations are analogous to POST, PUT, PATCH, or DELETE requests in RESTful APIs.
  3. Subscription: Used to establish a real-time connection between clients and servers to receive data updates over time.

These operations are sent to the GraphQL server as textual representations in the form of GraphQL documents. These documents adhere to the GraphQL syntax, which consists of fields, arguments, variables and directives. Clients send these documents to the server via an HTTP POST request to a designated GraphQL endpoint.

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