GraphQL vs. REST: A Complete Guide

APIs are the backbone of modern web and mobile applications. Almost every application on your phone and every website you visit uses APIs to fetch and interact with the data displayed on the screen. 

REST and GraphQL are two of the most common API design paradigms. This guide will explore the fundamental differences, benefits, and best use cases for both so you can choose which approach you like best for your own project or projects.

Hold on, what is an API?
If you are totally new to the concept of an API (Application Programming Interface), consider taking our Streamlined Data Ingestion with Pandas course. It will teach you how applications can leverage APIs to communicate with other programs - and vice versa - without either side knowing the details of each other’s inner workings. The course will make you an expert in the rules and protocols that applications use to request and exchange information.

What Is REST?

REST (Representational State Transfer) is an architectural style used to develop web services since the early 2000s. It defines a set of constraints and principles to build scalable and stateless APIs. REST APIs (also called RESTful APIs) are designed to be lightweight and can be used in any language or platform that supports HTTP.

If you are new to REST APIs, I would recommend getting used to interacting with them before developing your own. It will help you get a feel for how they work and what the best practices are. Have a look at Intermediate Importing Data in Python or Intermediate Importing Data in R to get started. Both courses have chapters on making HTTP requests, scraping the web, and other fun things. 

Key concepts of REST APIs

Let's try to understand the concepts of REST. 

Statelessness

Each interaction between the client and the server is independent. The server does not store any session data related to the client between requests, which means that every request from a client to a server must contain all the information needed to understand and process that request.

Resource-based

Every piece of data or functionality is treated as a resource that can be identified and manipulated through a unique identifier, typically a URI (Uniform Resource Identifier). 

For example, in an e-commerce application, resources might include customers, products, orders, etc. Every resource is identified by a unique URI that acts like an address where the resource can be accessed. For example:

• /products might refer to the collection of all products.

• /products/123 might refer to a specific product with the ID 123.

HTTP methods

RESTful APIs typically use standard HTTP methods to perform operations on resources:

• GET: Retrieve data from a server (e.g., fetch a list of products).

• POST: Submit data to the server (e.g., create a new product).

• PUT: Update an existing resource (e.g., modify product details).

• DELETE: Remove a resource (e.g., delete a product).

A standard GET request would look like this:

Example REST request and response. Image by Author.

REST APIs also use standard HTTP status codes to communicate errors, success, and other responses. And yes, status 418 I’m a teapot does exist!

Data Formats

A RESTful API can use different formats to represent and exchange data, including JSON, XML, HTML, Plain Text, YAML, and CSV.

What Is GraphQL?

GraphQL is an open-source query language and runtime for APIs that allows clients to request exactly the data they need, and nothing more. It was originally developed internally by Meta (previously Facebook) in 2012 to optimize data fetching for their mobile applications and released for public use in 2015.

Key concepts of GraphQL APIs

Let's look at the main ideas with GraphQL.

Client-specific queries

In GraphQL, clients define the structure of the response by specifying the fields they need in their queries. This means that the client can request only the specific data it requires, avoiding over-fetching (receiving too much data) and under-fetching (receiving insufficient data).

In GraphQL, a query to get a user’s detail would look like this:

Example GraphQL request and response. Image by Author.

Queries vs. mutations

While queries are used to read data, mutations are used to write or modify data. Mutations in GraphQL are analogous to the POST, PUT, and DELETE operations in REST.

Single endpoint

Unlike REST APIs, which might have multiple endpoints for different resources, a GraphQL API typically exposes a single endpoint. This endpoint handles all the queries and mutations, making it simpler for clients to interact with the API.

Strongly typed schema

GraphQL APIs are defined by a schema, which is a strongly typed definition of the data models available, and the relationships between them. This schema serves as a contract between the client and the server, ensuring that the data returned matches the client's request and is of the expected type.

Introspection

The GraphQL schema is self-documenting. Clients can use the introspection feature to query the schema itself and discover the types, queries, mutations, and subscriptions available, making it easier to explore and understand the API.

Real-time data

GraphQL supports real-time data updates through subscriptions. Subscriptions allow clients to receive updates whenever the data they are interested in changes, which is useful for real-time applications like chat apps or live feeds.

Key Differences Between GraphQL and REST

The table below summarizes the key differences between GraphQL and REST APIs.

As with most things in life, each solution has its advantages and inconveniences.

Choosing Between GraphQL and REST

The choice between REST versus GraphQL will depend entirely on your project’s needs. You probably already have an inkling based on the previous section, but as a rule of thumb, you should probably use REST when you have:

• Simple data models
• Applications requiring extensive caching.
• Teams familiar with REST conventions.
• Need for predictable, standardized responses.

And use GraphQL when you deal with:

• Complex data models with nested relationships.
• Applications needing flexible, dynamic queries.
• Rapid iteration and reduced backend adjustments.
• Real-time updates.

REST and GraphQL can also be used together in hybrid solutions, so your project can benefit from simple, well-defined REST endpoints but also from the flexibility of GraphQL for more complex data retrieval. For instance, in an e-commerce app, you could use REST for authentication and user registration to benefit from standard security practices like Oauth and use GraphQL to fetch more nested and complex information like product details, categories, and user reviews.

Conclusion

So you get it: both GraphQL and REST have their strengths and weaknesses and are suitable for different scenarios. The choice between them should be guided by your project’s requirements and the complexity of your data. 

That said, both tools are really fun to work with and can teach you a lot about data, so if you have the opportunity, I would recommend trying them out at some point!

And, if after reading this, you know what tool you want to use, then you are ready for the next step! Go check out our Mastering API Design: Essential Strategies for Developing High-Performance APIs blog post to learn how to design your own APIs.