Introduction to GraphQL

Part 1: From REST API to GraphQL

GraphQL was developed by Facebook in 2012 and was released as an open-source project in 2015. It has since become a popular alternative to REST APIs, especially for complex data-fetching scenarios.

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What is GraphQL?

GraphQL is a query language for our API and a server-side runtime for executing queries using a type system we define for our data.

Terminologies

• Schema: The core of any GraphQL service, defining the types and the relationships between them.
• Query: A read-only fetch operation.
• Mutation: A write operation that allows us to insert, update, or delete data.
• Subscription: Allows clients to subscribe to real-time updates.
• Resolvers: Functions that handle fetching the data for each type in a schema.

💡 The correct term for the component that defines and serves the GraphQL schema is typically called the GraphQL Server or API Server.

Example from Octopus Energy API:

query EnergyProductQuery($productCode: String!) {
    energyProduct(code: $productCode) {
        code
        fullName
        displayName
        description
        term
    }
}