What Is GraphQL?

You've been building REST APIs — one endpoint for users, another for posts, another for comments. The client makes three requests, stitches the data together, and half of it gets thrown away because it wasn't needed in the first place. GraphQL was built to fix exactly that. It gives the client full control over what data it receives. One request. Exactly what you asked for. Nothing more, nothing less. The Problem REST Couldn't Solve Before understanding GraphQL, you need to understand the two problems that drove its creation. Over-fetching The server returns more data than the client needs. GET /users/123 Response: { "id": 123, "name": "Anne", "email": "anne@example.com", "phone": "...", "address": "...", "createdAt": "...", ← you didn't need any of this "updatedAt": "..." ← but the server sent it anyway } The client only needed name and email — but it downloaded the whole object every time. Under-fetching One endpoint doesn't return enough, so the client has to make multiple requests. GET /users/123 → gets the user GET /users/123/posts → gets their posts GET /users/123/followers → gets their followers Three round trips to the server just to render one screen. On a mobile network, that cost is real. GraphQL's answer: Let the client write the query. The server returns exactly what was asked. What Is GraphQL? GraphQL is a query language for your API and a runtime for executing those queries. It was created by Facebook in 2012, open-sourced in 2015, and is now maintained by the GraphQL Foundation . Unlike REST, which exposes multiple URL endpoints, GraphQL exposes a single endpoint — typically POST /graphql . The client sends a query in the request body describing exactly what it wants, and the server responds with only that data. Key characteristics: Single endpoint — everything goes through POST /graphql Client-driven — the client defines the shape of the response Strongly typed — every field has a declared type in the schema Introspective — clients can query the API