What is Apollo Server used for?

Apollo Server is used to build the backend of a GraphQL API in Node.js, defining a schema and resolvers that determine how queries are executed against underlying data sources.

Does Apollo Server require Express?

No. Apollo Server can run standalone or integrate with Express, Fastify, and other Node.js HTTP frameworks, depending on how a project is structured.

What is schema-first development?

Schema-first development means defining the GraphQL API's types and operations in SDL first, then implementing resolver functions to fulfill that contract, which helps frontend and backend teams agree on an API shape early.

Can Apollo Server be used with Apollo Federation?

Yes, Apollo Server can act as a federated subgraph, allowing multiple independently deployed Apollo Server instances to be composed into one unified GraphQL API.

Is Apollo Server free?

Yes, Apollo Server is open source and free to use under its published license.

What is a resolver in Apollo Server?

A resolver is a function that returns the data for a specific field in the GraphQL schema, whether that means querying a database, calling another API, or computing a value.

Web

Apollo Server

By Apollo GraphQL, Inc.

IntermediateFramework10K learners

js that lets developers define a schema and resolvers to build production-ready GraphQL APIs, as part of the broader Apollo GraphQL platform.

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Definition

Apollo Server is an open-source, spec-compliant GraphQL server library for Node.js that lets developers define a schema and resolvers to build production-ready GraphQL APIs, as part of the broader Apollo GraphQL platform.

Overview

Apollo Server implements the official GraphQL specification on top of Node.js, and can run as standalone middleware or be mounted onto existing HTTP frameworks such as Express.js or Fastify. Development follows a schema-first approach: developers define types and operations using GraphQL's Schema Definition Language (SDL), then write resolver functions that fetch or compute the data for each field. Beyond basic query execution, Apollo Server supports Apollo Federation, letting a service act as one "subgraph" that gets composed with others into a larger unified API managed by Apollo GraphQL's gateway. Its plugin system adds capabilities like response caching, performance tracing, and custom error formatting, and it includes TypeScript support along with an interactive schema explorer (Sandbox) for testing queries during development. Apollo Server is commonly paired with Apollo Client or other GraphQL clients consuming the API from React or other frontend applications.

Key Features

Spec-compliant GraphQL query execution engine
Schema-first development with SDL and resolver functions
Integrates with Express, Fastify, or runs standalone
Apollo Federation support for building composable subgraphs
Plugin system for caching, tracing, and error handling
First-class TypeScript support
Built-in schema explorer for interactive testing

Use Cases

Building GraphQL APIs for web and mobile clients

Exposing a unified API layer over multiple microservices via federation

Replacing or supplementing REST endpoints

Rapidly prototyping backend APIs

Powering data layers for React or Vue frontends

Frequently Asked Questions

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