When building APIs, you have to choose between different approaches. REST has been the standard for years, but GraphQL has gained a lot of popularity. I've used both, and each has its strengths. The key is understanding when to use which one.

REST, or Representational State Transfer, is an architectural style that's been around for a while. It uses HTTP methods like GET, POST, PUT, and DELETE to interact with resources. Each resource has a URL, and you make requests to those URLs to get or modify data.

GraphQL is a query language and runtime for APIs. Instead of multiple endpoints, you have a single endpoint. Clients send queries that specify exactly what data they need, and the server returns only that data.

The REST approach

REST is simple and familiar. Most developers understand how REST APIs work. You have endpoints like /users, /posts, and /comments. To get a user, you make a GET request to /users/123. To get a user's posts, you might make a request to /users/123/posts.

REST follows HTTP conventions, which means you can leverage HTTP caching, status codes, and other HTTP features. Browsers and proxies understand REST APIs, which can help with caching and performance.

The downside of REST is that you often need multiple requests to get all the data you need. If you want a user and their posts and comments, you might need to make three separate requests. This can be slow, especially on mobile networks.

REST also tends to over-fetch or under-fetch data. An endpoint might return more data than you need, or you might need to make additional requests to get related data. This isn't always a problem, but it can be inefficient.

The GraphQL approach

GraphQL solves the over-fetching and under-fetching problems. You write a query that specifies exactly what fields you need, and the server returns only those fields. If you need a user's name and email, you get just that. If you need a user with their posts and comments, you can get it all in one request.

GraphQL has a single endpoint, usually /graphql. All queries go to this endpoint, which simplifies things. You don't need to design multiple endpoints for different use cases.

The GraphQL schema serves as documentation. The schema defines what data is available and what operations you can perform. Tools can introspect the schema and generate documentation automatically.

The downside is that GraphQL is more complex. You need to learn the query language, and you need to set up resolvers on the server side. Caching is also more complicated because all requests go to the same endpoint.

When to use REST

REST is a good choice for simple CRUD operations. If you're building a straightforward API where clients need to create, read, update, and delete resources, REST is simple and effective.

REST also works well when you want to leverage HTTP caching. If your data doesn't change often, HTTP caching can significantly improve performance. REST's use of URLs and HTTP methods makes this straightforward.

If your team is already familiar with REST, there's value in sticking with what you know. The learning curve for GraphQL might not be worth it if REST meets your needs.

When to use GraphQL

GraphQL shines when you have complex data requirements. If clients need to fetch related data from multiple sources, GraphQL's ability to get everything in one query is valuable.

GraphQL is great for mobile applications where reducing the number of requests is important. Mobile networks can be slow, so getting all the data you need in one request can make a big difference.

If you have multiple clients with different data needs, GraphQL lets each client request exactly what it needs. A mobile app might need minimal data, while a web dashboard might need more detailed information. Both can use the same GraphQL API.

Hybrid approaches

You don't have to choose one or the other. Many applications use both. You might use REST for simple operations and GraphQL for complex queries. Or you might use GraphQL internally but expose a REST API for external clients.

The important thing is to choose based on your needs, not on what's trendy. Both REST and GraphQL are valid choices, and the right one depends on your specific situation.

Performance considerations

REST can be faster for simple operations because there's less overhead. A simple GET request is straightforward and fast. But if you need multiple requests, the overhead adds up.

GraphQL can be faster when you need complex data because you get everything in one request. But GraphQL queries can be expensive on the server side if not optimized. A query that fetches a lot of nested data might require multiple database queries.

Both approaches can be optimized. REST APIs can use HTTP caching and pagination. GraphQL can use data loaders to batch database queries and reduce the N+1 query problem.

The bottom line

REST and GraphQL are both valid choices for building APIs. REST is simpler and more familiar, which makes it a good default choice. GraphQL is more powerful for complex data requirements, but it adds complexity.

Start with REST if you're not sure. It's simpler, and you can always add GraphQL later if you need it. Don't choose GraphQL just because it's newer or seems more powerful. Choose it because it solves a specific problem you have.

The best API is the one that meets your needs with the least complexity. Sometimes that's REST, sometimes it's GraphQL, and sometimes it's a combination of both.