As applications become more complex and interconnected, APIs need to evolve to meet new demands. Two popular API design approaches are REST and GraphQL. REST (Representational State Transfer) has been the dominant architectural style for web APIs over the past decade. But recently, GraphQL has emerged as a modern alternative to REST for building APIs. In this article, we’ll compare GraphQL and REST to understand the relative strengths and weaknesses of each approach.
What is REST?
REST (Representational State Transfer) is an architectural style for building scalable web APIs. It uses HTTP requests to access and manipulate resources. Resources are represented as URIs (like https://api.example.com/users/1234), and can be accessed or modified using HTTP methods like GET, POST, PUT, and DELETE.
Some key principles of REST include:
- Stateless – No client context is stored on the server between requests
- Client-server separation of concerns – Client handles the UI, server handles the data
- Cacheable data – Responses specify if they can be cached to improve performance
- Uniform interface – Resources are manipulated predictably using HTTP methods
- Layered system – Requests/responses can traverse intermediaries like caches and load balancers
REST uses a resource-oriented approach that makes APIs intuitive and easy to use. It’s been widely adopted for public APIs and has a large community of developers experienced with building and consuming REST APIs.
What is GraphQL?
GraphQL is a query language for APIs created by Facebook in 2012. Unlike REST, GraphQL exposes a single endpoint that accepts queries for specific data a client needs. The structure of the data is defined using a schema. Clients can access nested, relational data in a GraphQL API with a single roundtrip to the server. Some key features of GraphQL include:
- Strongly typed schema – Defines the API surface using a hierarchical type system
- Client-specified queries – Clients request exact data requirements in queries
- Hierarchical nested data – Related data can be queried in a single request
- Breaking changes can be avoided – New fields/types can be added without breaking existing queries
- Powerful developer tools – GraphiQL explorer, auto complete, schema introspection
GraphQL simplifies clients by moving complexity into the server implementation. The schema serves as the contract between the client and server. GraphQL APIs provide flexibility and efficiency for evolving application requirements.
Comparing GraphQL and REST
Now that we’ve introduced REST and GraphQL, let’s compare them across some key factors:
Fetching Data
Getting data from a REST API requires separate requests to multiple endpoints. For example, displaying user profile information might require requesting data from /users, /posts, and /comments. GraphQL allows clients to retrieve connected data in a single request using nested queries. The GraphQL server handles aggregating and returning the different resources. This can significantly reduce the number of roundtrips to fulfill a given request.
Over- and under-fetching
With REST, clients often end up retrieving more data than needed or making multiple roundtrips to fetch additional data. GraphQL solves these issues by enabling the client to specify their precise data requirements. Only requested fields are returned so there is no over-fetching. Related data can be queried in the same request so there is no under-fetching.
Versioning
REST APIs typically version via the URL – for example, /v1/users vs /v2/users. This puts the burden on clients to updated URLs when APIs change. GraphQL APIs are versioned based on the schema. Schemas can be updated without affecting existing queries. New types and fields can be added without impacting existing clients.
Caching
Caching improves performance by avoiding repeated requests for the same data. With REST, clients cache responses. If data is updated on the server, the client may end up with stale data. GraphQL uses a normalized caching model. Clients cache query results based on arguments and fields. When data changes on the server, previously cached requests are not affected since they are unique queries.
Documentation
REST APIs use external documentation like OpenAPI specs to describe API structure. The GraphQL schema serves as built-in documentation by defining types and fields. Tools like GraphiQL also provide interactive documentation to explore schemas.
Endpoints
REST requires separate endpoints for every resource and operation. GraphQL exposes a single endpoint for all queries, mutations, and subscriptions. The endpoint receives requests and routes them to appropriate resolver functions.
API Development
Developing a REST API requires identifying and modeling resources as well as implementing endpoints for each one. GraphQL APIs involve defining the schema first and then implementing corresponding resolvers. The GraphQL schema already outlines the API structure.
When to use REST vs GraphQL
Given their differences, here are some guidelines on when to use a REST vs GraphQL architecture:
- Use REST for:
- Simple, static data models
- Public APIs needing caching
- Microservices with few complex data dependencies
- Use GraphQL for:
- Frequent, complex data queries
- Apps needing rapid product iteration
- Integrating multiple data sources
- APIs powering dynamic client applications
GraphQL tends to work better for evolving internal APIs, while REST may be preferable for public APIs. In some cases, REST and GraphQL can be combined by having a REST wrapper around a GraphQL implementation.
Conclusion
Here is a summary of the key differences between REST and GraphQL:
| REST | GraphQL | |
|---|---|---|
| Fetching Data | Multiple round trips required | Single round trip for nested data |
| Over/under fetching | Common issues | Precise field selection |
| Versioning | Based on endpoints | Based on schema |
| Caching | Cached responses | Normalized caching |
| Documentation | External docs required | Self-documenting schema |
| Endpoints | Multiple endpoints | Single endpoint |
| Development | Model resources first | Define schema first |
In summary, GraphQL enables more efficient data fetching compared to REST. It provides flexibility and reduces complexity for client developers. For many modern applications with dynamic data requirements, GraphQL presents clear advantages over REST. However, REST continues to be a solid choice for straightforward scenarios like public APIs. When evaluating API approaches, consider factors like use cases, complexity, and rate of change. With a strong understanding of both GraphQL and REST, you can determine the best fit for your specific API needs.