GraphQL vs REST: API Design Choice Guide

What is REST API?

REST (Representational State Transfer) is an API architectural style built on HTTP protocol. Resources are identified by URIs.

Each endpoint represents a specific resource or collection: GET /users, GET /users/123, POST /users.

CRUD operations are performed with HTTP methods (GET, POST, PUT, DELETE). Response format is usually JSON.

REST is based on stateless, cacheable, and uniform interface principles. Uses all HTTP features (caching, status codes).

What is GraphQL?

GraphQL is a query language and runtime developed by Facebook. The client queries exactly the data it needs.

Single endpoint: /graphql. Client specifies which fields it wants in the query. Server returns only the requested fields.

Schema: API's type system. Data model is defined with type definitions. Query, Mutation, and Subscription types.

Resolver: Functions that access data source for each field. Data can be fetched from database, REST API, microservice, etc.

Comparison: Advantages and Disadvantages

Over-fetching/Under-fetching: REST returns unnecessary data (over-fetching) or insufficient data (under-fetching). GraphQL returns exactly the requested data.

Single request: Multiple resources can be fetched in a single request with GraphQL. Multiple requests needed with REST.

Caching: REST naturally supports HTTP caching (Cache-Control, ETag). Caching is more complex in GraphQL (persisted queries, Apollo cache).

Learning curve: REST is learned with HTTP knowledge. GraphQL requires new concepts like schema, resolver, query language.

Tooling: Postman, Swagger for REST. GraphiQL, Apollo Studio for GraphQL. Both have good tooling ecosystems.

Use Cases

Prefer REST: Simple CRUD APIs, public APIs, when caching is important, when bandwidth is limited for mobile apps.

Prefer GraphQL: Complex data requirements, multiple frontends (web, mobile, desktop), microservices aggregation, real-time subscriptions.

Hybrid approach: REST for public API, GraphQL for internal/federation. Some companies use both together.

BFF (Backend for Frontend): Separate GraphQL layer for each frontend. Different queries for web and mobile.

Performance Comparison

REST: HTTP caching, CDN support, simple load balancing. Each endpoint can be cached independently.

GraphQL: N+1 problem (solved with DataLoader), query complexity analysis, caching with persisted queries.

Bandwidth: GraphQL prevents unnecessary data transfer. Provides bandwidth savings for mobile apps.

Latency: REST may require multiple round-trips. GraphQL gets all data in a single request. However, complex queries can be slow on server side.

Selection Criteria

Team experience: REST is more common and known. GraphQL requires more learning.

API consumers: REST for public API (wider compatibility). GraphQL for internal API (more flexibility).

Data complexity: REST for simple data models. GraphQL for complex, related data models.

Caching requirement: REST for heavy caching. GraphQL subscriptions for real-time data.

Migration: Wrap existing REST API with GraphQL (schema stitching, federation). Make gradual transition.