GraphQL

GraphQL is a query language for APIs and a runtime for executing those queries with your existing data.

Tools for implementing GraphQL include GraphQL.js, Apollo and Relay.

Features:

• Declarative Data Fetching: Clients can request exactly the data they need
• Versionless API: Fields can be added without breaking existing queries
• Single Endpoint: Handles all requests (unlike REST APIs)
• Real-time Capabilities: Clients can subscribe for updates when data changes
• Strongly Typed Schema: Specifies types of data that can be queried
• Introspection: Clients can query the schema (making the API self-documenting)

Use Cases:

• Aggregation of data from multiple sources
• Minimization of over-fetching or under-fetching of data
• API needs to evolve over time without breaking existing clients

{
  user(id: "1") {
    name
    email
    posts(limit: 2) {
      title
      content
    }
  }
}

{
  "data": {
    "user": {
      "name": "John Doe",
      "email": "john@example.com",
      "posts": [
        {
          "title": "GraphQL Basics",
          "content": "This is a post about GraphQL."
        },
        {
          "title": "Advanced GraphQL",
          "content": "This is a post about advanced GraphQL topics."
        }
      ]
    }
  }
}