What is GraphQL?
GraphQL is an open-source data query and manipulation language for APIs, developed by Facebook in 2012 and released publicly in 2015. Unlike REST, where each resource has its own endpoint (e.g., /users, /posts), GraphQL lets clients request exactly the data they need through a single endpoint.
In simple terms, GraphQL gives you precise control over your data requests and helps avoid over-fetching or under-fetching data.
Why Use GraphQL Over REST?
GraphQL addresses several pain points developers often encounter with REST APIs:
1. One Endpoint to Rule Them All
With REST, you may need to hit multiple endpoints to assemble a complete data view. In contrast, GraphQL uses one endpoint to fetch data from multiple sources in a single request.
2. Avoid Over-fetching and Under-fetching
In REST, a request to /users might return all user fields, even if you only need the name and email. GraphQL allows clients to specify exactly what they need—and nothing more.
3. Better Developer Experience
GraphQL includes introspection, meaning you can explore the schema and types programmatically. Tools like GraphiQL and Apollo Studio make it easy to write, test, and debug queries.
4. Real-time Data with Subscriptions
While REST supports real-time data through webhooks or polling, GraphQL has built-in support for subscriptions that allow real-time data streaming through WebSockets.
How GraphQL Works
At its core, GraphQL is about types, queries, and resolvers.
1. Schema Definition
GraphQL uses a Schema Definition Language (SDL) to define the structure of your API. For example:
type User {
id: ID!
name: String!
email: String!
}
type Query {
user(id: ID!): User
}
This schema defines a User type and a Query type that allows fetching a user by ID.
2. Queries
Here's a simple query to fetch a user's name and email:
query {
user(id: "123") {
name
}
}
Unlike REST, you're not tied to specific endpoints—you define what data you want, and GraphQL gives you just that.
3. Resolvers
Resolvers are functions that map a query to your underlying data sources (e.g., databases, services).
const resolvers = {
Query: {
user: (_, { id }) => getUserFromDB(id),
},
};
Resolvers are what actually run the logic to return data for each field in the query.
Setting Up a Simple GraphQL Server
To build a basic GraphQL server in Node.js using Apollo Server:
npm install apollo-server graphql
Then:
const { ApolloServer, gql } = require('apollo-server');
const typeDefs = gql`
type User {
id: ID!
name: String!
email: String!
}
type Query {
user(id: ID!): User
}
`;
const resolvers = {
Query: {
user: (_, { id }) => ({ id, name: 'Jane Doe', email: '[email protected]' }),
},
};
const server = new ApolloServer({ typeDefs, resolvers });
server.listen().then(({ url }) => {
console.log(`???? Server ready at ${url}`);
});
Visit the server URL and use the GraphQL playground to test your queries.
Common Use Cases for GraphQL
- Mobile and web apps: Optimized data fetching means faster load times and lower bandwidth usage.
- Microservices: GraphQL can act as a gateway, unifying multiple services behind a single API.
- Real-time apps: Subscriptions allow you to push live updates to users.
GraphQL vs REST: Summary
| Feature | REST | GraphQL |
| Endpoints | Multiple | Single |
| Data Fetching | Fixed structure | Client-defined |
| Over-fetching | Common | Avoided |
| Tooling | Basic | Advanced |
| Real-time support | Manual setup | Native via subscriptions |
Final Thoughts
GraphQL isn’t a silver bullet—it can be overkill for simple applications or where caching is critical. But if your app needs flexibility, real-time updates, or aggregated data, GraphQL is a powerful alternative to REST.
Whether you're a backend developer, frontend engineer, or full-stack enthusiast, learning GraphQL can greatly improve your efficiency in API communication.
Read more on- https://keploy.io/blog/community/exploring-graphql-api-development