REST and GraphQL are two popular architectural approaches for building APIs. REST has been the industry standard for decades, while GraphQL, developed by Facebook, offers a more flexible, query-driven alternative. Understanding their trade-offs helps you choose the right tool for your use case.
REST (Representational State Transfer) is an architectural style where resources are exposed as fixed URLs called endpoints. Each endpoint returns a predetermined data shape; for example, GET /users/42 always returns the full user object. REST leverages standard HTTP methods — GET, POST, PUT, DELETE — and status codes, making it universally understood by clients and infrastructure alike.
GraphQL is a query language and runtime for APIs, letting clients specify exactly what data they need in a single request. Instead of many resource-specific endpoints, GraphQL exposes one endpoint (typically POST /graphql) that accepts structured queries. Facebook open-sourced it in 2015 to solve over-fetching and under-fetching problems common in REST.
Over-fetching happens when a REST endpoint returns more fields than the client needs, wasting bandwidth. Under-fetching happens when one endpoint does not return enough data, forcing multiple sequential requests — known as the N+1 problem. GraphQL eliminates both issues by letting the client declare exactly the fields and nested relationships it requires in one round trip.
A GraphQL schema defines Types, Queries (reads), Mutations (writes), and Subscriptions (real-time). The server maps each field to a resolver function that fetches or computes the value. When a client sends a query, the GraphQL engine traverses the schema, calls the relevant resolvers, and assembles the response into a JSON object that mirrors the query shape exactly.
REST is simpler to cache at the HTTP layer because each endpoint has a stable URL, making CDN and browser caching straightforward. GraphQL queries are POST requests by default, which breaks HTTP caching out of the box — though tools like persisted queries and Apollo Client mitigate this. Choose REST for public, resource-oriented APIs with predictable access patterns; choose GraphQL when clients have diverse or complex data requirements, such as in mobile apps where bandwidth efficiency matters.
In GraphQL, naive resolver implementations cause the N+1 database query problem — use a batching tool like Facebook's DataLoader to group and cache database calls. Always enforce query depth and complexity limits on public GraphQL endpoints to prevent denial-of-service via deeply nested queries. For REST, version your API (e.g., /v1/, /v2/) to evolve it without breaking existing clients; GraphQL handles evolution through schema deprecations instead, avoiding versioning entirely.
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