GraphQL: A Beginner’s guide

If you’ve ever dabbled in web development, you’ve probably come across REST (Representational State Transfer) APIs. While REST has been the most popular way to build APIs for years, there’s a new player in town that’s changing the way we interact with data. This is GraphQL.

But wait a minute, what is GraphQL? Why is it so popular and how can it make your life as a developer easier? Then you’ve come to the right place to find out. In this blog post, we’ll dive deep into GraphQL and explain the core concepts, the difference to REST and, most importantly, how you can start using it today.

What is GraphQL?

At its core, GraphQL is a query language for your APIs, but it’s much more than that. It was developed by Facebook in 2012 and released in 2015. GraphQL was designed to make your API requests more efficient, flexible and powerful.

Think of it like this: You use REST to request specific data via different endpoints. You could click the /users endpoint to get a list of users, and then another endpoint /posts to retrieve their posts. This works, but often provides more information than you need, or you may even have to make multiple requests to get everything you want.

GraphQL solves this problem by allowing you to retrieve exactly what you want with a single query. It’s like going to a restaurant and ordering a customized meal instead of choosing something ready-made from the menu.

Why GraphQL? The advantages you need to know

So why should you bother with GraphQL? What makes it such a big deal?

1. You get exactly what you need – no more, no less

One of the most frustrating things about REST is retrieving too much or too little data. With REST, you may end up retrieving more data than you need at one endpoint, making the response bigger and slower. But it can also happen that you get too little data and have to go to another endpoint.

With GraphQL, you can query exactly the data you need with a single request, no more and no less. For example, if you only need the name and email address of a user, you can specify only these fields in your request. This saves bandwidth and makes your API requests much more efficient.

2. Reduce the number of API calls

With a traditional REST setup, multiple requests are often required to retrieve related data. You may need to retrieve users from one endpoint and related posts from another. With GraphQL, you can retrieve both users and their contributions in a single request. This reduces overhead on the client and server and improves performance.

3. Strongly typed schema

GraphQL APIs are based on a strongly typed schema. This schema serves as a contract between the client and the server. It defines all possible queries, mutations and the form of the data. When you make a query, you can be sure that the returned data matches the schema. This reduces errors as they are recognized early on, even before you make a query.

4. Self-documentation

One of the best features of GraphQL is that it is self-documenting. Because of the strongly typed schema, you can use tools like GraphiQL (an in-browser IDE for executing queries) to explore the API and see what’s available. This means you don’t have to spend hours reading through the API documents — GraphQL shows you what’s possible in real-time.

5. Easy development without versioning

With REST, you often have to version your API when you make changes. For example, if you need to add a field to your response, you can introduce a new version of the endpoint. GraphQL is more flexible in this regard. Since you only query the fields you need, new fields can be added to the schema without breaking existing clients. This makes it easier to evolve your API over time.

How does GraphQL work?

Now that you’re convinced of the benefits, let’s take a closer look at how GraphQL works. At its core, GraphQL is about three key concepts: Queries, mutations and subscriptions.

1. Queries: retrieving data

A query in GraphQL is the way in which you retrieve data. In a REST API, you would make a GET request to an endpoint like /users. In GraphQL, you send a query in which you specify exactly what data you want and how it should be structured.

Here is an example of a simple query:

{
user(id: "1") {
name
email
posts {
title
body
}
}
}

This query asks for a user’s name and email address as well as the title and text of their posts. Note that the query is very specific about what data it needs — no more excessive retrieval.

2. Mutations: Changing data

Queries are used to retrieve data, but sometimes you need to change data. This is where mutations come into play. Mutations allow you to create, update or delete data in your API.

Here is an example of a mutation to add a new post:

mutation {
addPost(title: "GraphQL is Awesome", body: "Here’s why…", userId: "1") {
id
title
body
}
}

This mutation adds a new post and returns the ID, title and body of the newly created post.

3. Subscriptions: Data in real time

GraphQL also supports real-time updates through subscriptions. With subscriptions, you can listen for specific events and be notified when they occur. This is perfect for use cases like real-time chat apps or live sports scores.

Here is an example of a subscription:

subscription {
newMessage {
id
content
sender {
name
}
}
}

In this case, you will receive the content of the message and the name of the sender each time a new message is sent.

GraphQL vs. REST: The most important differences

It’s hard to talk about GraphQL without comparing it to REST, since REST has been the dominant API paradigm for so long. So how exactly does GraphQL differ from REST and when should you choose one over the other?

1. Flexible Queries vs. fixed endpoints

With REST, you have fixed endpoints for different resources. For example, /users returns a list of users and /posts returns a list of posts. You are limited by the structure of the individual endpoints and often have to make multiple requests to get all the data you need.

With GraphQL, on the other hand, you can query exactly what you want. There are no fixed endpoints, but a single GraphQL endpoint where you can specify what data you need and how it is structured.

2. Efficient data retrieval

With REST, over- and under-fetching is a common problem. You often get more data than you need, or not enough, so you have to make multiple requests. GraphQL solves this problem by allowing you to retrieve exactly what you need in one go. This makes it particularly useful for mobile applications and situations where bandwidth is limited.

3. Versioning

Versioning is a common problem with REST APIs. If you need to make changes to an API, such as adding a new field, you often need to create a new version of the API. This can quickly become confusing, as different clients use different versions.

GraphQL eliminates the need for versioning. Since clients only request the fields they need, new fields can be added to the schema without breaking existing clients.

4. Self-documenting

REST APIs usually require their own documentation. You may need to look at an API specification or read through the documentation to understand what is available. GraphQL APIs, on the other hand, are self-documenting. With tools like GraphiQL, you can explore the API in real time, making it easier to understand what data is available.

Set up a GraphQL server: Your first steps

Now that you understand the theory, let’s dive into the practice. How do you set up a GraphQL server? Don’t worry, it’s easier than it sounds.

We use Node.js and a library called Apollo Server, which makes setting up a GraphQL server a breeze.

Step 1: Install dependencies

First, you need to have Node.js installed. Then, in your project directory, run the following command to install Apollo Server and GraphQL:

npm install apollo-server graphql

Step 2: Define your schema

Next, you need to define the schema for your API. The schema describes the shape of your data and the available queries and mutations. Here is a simple example:

const { ApolloServer, gql } = require('apollo-server');

const typeDefs = gql type Query { hello: String } ;

const resolvers = {
Query: {
hello: () => 'Hello, world!
},
};

const server = new ApolloServer({ typeDefs, resolvers });

server.listen().then(({ url }) => {
console.log(🚀 server ready at ${url});
});

This is a simple GraphQL server with a single query that returns “Hello, world!”. The typeDefs define the schema and the resolvers define how the data should be fetched.

Step 3: Start your server

Start your server with the following command:

node index.js

You should see something like this in the terminal:

🚀 Server ready at http://localhost:4000/

You can now navigate to this URL in your browser and start queries against your GraphQL API!

Step 4: Extend your API

Of course, you’ll want to create something more complex than a single “Hello, world!” query. To do this, you can define more types, queries and mutations in your schema.

Here’s an example of a more complex schema with users and posts:

const typeDefs = gql`
type User {
id: ID!
name: String!
email: String!
posts: [Post]
}

type Post {
id: ID!
title: String!
body: String!
}

type Query {
users: [User]
user(id: ID!): User
}

type Mutation {
addUser(name: String!, email: String!): User
addPost(title: String!, body: String!, userId: ID!): Post
};

In this example, we’ve added users and posts to the schema, along with queries to retrieve users and a mutation to add new users and posts. You can then create resolvers for each query and mutation to interact with your data.

Best practices for using GraphQL

When you start building your GraphQL API, you should follow some best practices to ensure that your API is efficient, scalable and easy to use.

1. Keep your schema simple

It’s tempting to pack everything into your GraphQL schema, but try to keep it simple. A well-structured schema should be easy to understand and use. Break your schema down into smaller, logical pieces to keep it maintainable.

2. Use pagination and batching

Just because GraphQL can return a lot of data in a single query doesn’t mean you should abuse it. Implement pagination for large data sets to avoid retrieving too much data at once. This improves performance and makes your API more efficient.

3. Implement caching

GraphQL queries can be complex, so caching is essential to reduce the load on your server. Tools like Apollo Client have built-in caching mechanisms, but you should also consider server-side caching strategies for larger applications.

4. Monitor and log your Queries

Since GraphQL allows clients to request custom data structures, you should monitor which queries are executed most frequently and log inefficient or slow queries. This will allow you to optimize your API over time.

5. Use authentication and authorization

Since GraphQL can expose a lot of data, it is important to secure your API. Implement authentication and authorization to ensure that only authorized users can access certain queries or mutations.

Conclusion: Is GraphQL right for you?

GraphQL is an incredibly powerful tool that can make your API more flexible, efficient and user-friendly. If you’re tired of the limitations of REST and are looking for a way to query your data more intelligently, GraphQL is definitely worth exploring.

Whether you’re developing a mobile app with limited bandwidth or a large-scale application with complex data requirements, GraphQL can help you optimize your API requests and improve performance.

But like any technology, GraphQL is not a panacea. It’s important to consider the specific requirements of your project before committing to it. In some cases, a well-structured REST API may still be the best choice. But if you need flexibility, efficiency and strong typing, GraphQL may be just the solution you’ve been looking for.

Now it’s your turn! Give it a try, set up your first GraphQL server and find out how it can make your life easier. Have fun programming!