What is GraphQL?

What is GraphQL?

GraphQL is a query language and runtime where API clients explicitly describe the fields they need. In REST, data is often gathered from several resource URLs; in GraphQL, the client sends a schema-valid query to a single endpoint.

For example, a product detail screen can request only the product name, price, stock level, and first three reviews. The server resolves those fields and returns a JSON response with that shape.

How Does It Work?

A GraphQL API publishes a schema that defines types, queries, mutations, and subscriptions. The client sends a query against that schema; the server validates it, collects data through resolver functions, and returns JSON.

The main operation types are:

• Query: Reads data
• Mutation: Creates, updates, or deletes data
• Subscription: Listens for real-time events

Business Use

GraphQL is useful when mobile apps, dashboards, customer portals, and third-party integrations consume the same data model in different shapes. By avoiding unnecessary fields, it can make complex screens more efficient over the network.

It does not automatically replace a REST API. File downloads, simple CRUD, and cache-friendly resource structures may remain simpler with REST. A well-designed API using GraphQL needs authorization, query complexity limits, and observability from the start.