What is GraphQL? Components, Pros and Cons

While working on web or mobile applications, you must have heard about GraphQL. It is one of the most famous technologies that is used to manage data between the client and the server. You might wonder, what is GraphQL, and how it differs from other APIs like REST. In this blog, you will understand what is GraphQL, how it works, its key features, and how it is different from other REST APIs.

Table of Contents:

• What is GraphQL?
• Key Components of GraphQL
• How Does GraphQL Work?
• Advantages of GraphQL
• Disadvantages of GraphQL
• GraphQL vs REST API
• Conclusion

What is GraphQL?

GraphQL is basically a query language for APIs and a runtime that uses a schema to define how data is structured and retrieved. It was developed by Facebook in 2012 and open-sourced in 2015. Since then, it has been widely used by companies like GitHub, Shopify, and Twitter.  It helps you to request only the data that you need, and nothing else. In simple terms, GraphQL gives you more control over how your application fetches data from the server. Instead of multiple endpoints like in REST APIs, you just need to send a single query to one endpoint, and you will get back exactly what you ask. 

Key Features of GraphQL

1. Flexible Queries: With the help of GraphQL, you can ask for the exact data that you need, so that you don’t get anything extra and don’t miss out on anything important.

2. Clear Data Structure: It uses a defined structure (called a schema) that clearly indicates what kind of data is available. This helps to identify errors easily.

3. Live Data Updates: It also provides you with real-time updates when there are any changes in data. It is a great choice for building chat apps or dashboards.

4. One Endpoint: It uses only a single URL rather than making separate calls to separate sets of data, like in REST, although you do need a server.

5. Schema Exploration: You can check what data and operations are available in the API using special queries, without needing any separate documentation.

6. Group separate requests into one: With the help of GraphQL, you can group separate requests into one. This helps you reduce the number of times your app interacts with the server.

Key Components of GraphQL

In order to understand GraphQL better, let us have a look at some of its main components that help it to work properly.

1. Schema

The Schema is the backbone of any GraphQL API. It defines the kind of data you can request and how it is structured. It lists available data types like users, products, or posts, along with their details and relationships. Each piece of data in the schema has a specific type, such as String, Int, or Boolean, to keep everything organized and error-free. The schema is also used to define root types Query (to read data), Mutation (to modify data), and Subscription (to get real-time updates). These root types act as the main entry points for interacting with a GraphQL API.

2. Query

GraphQL queries are the way you ask the server for specific data. You have to write a query that tells the server exactly what information is needed. The thing that makes it special is that the server will respond with data that follows the same structure that you asked for. Unlike REST APIs, where you often get a lot of unnecessary data, GraphQL ensures that you get what you ask for. This helps to keep things clean and efficient.

Example of a simple query:

{
  user(id: "1") {
    name
    email
  }
}

The above query is used to ask for the name and email of the user with ID 1.

Example of a nested query:

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

Here, you not only get the user’s name and email but also their posts and each post’s comments. Nested queries allow you to fetch related data in a single request, making data retrieval more efficient.

3. Types

Types in GraphQL are used to define the shape of your data in the schema, specifying what can be sent or received. Scalar types are basic values like String, Int, Float, Boolean, and ID. Object types group related fields, enums define fixed sets of values, and input types are used for sending data via mutations. Union and interface types allow fields to return multiple types or enforce shared structures.

4. Mutation

Mutations are used when you want to add, update, or delete data, while queries focus on retrieving it. This includes actions like creating a new record, updating existing information, or deleting something from the database. Mutations are similar to queries, but they usually take input and return the result after the change is made, allowing you to see what was added or updated. They can also include nested mutations to handle related data in a single request, and you can implement error handling to capture issues like validation errors or failed updates.

Example of a simple mutation:

mutation {
  addUser(name: "xyz", email: "[email protected]") {
    id
    name
  }
}

The above code adds a new user and then returns their ID and name.

Example of a nested mutation with error handling:

mutation {
  addUser(name: "xyz", email: "[email protected]") {
    id
    name
    posts {
      create(title: "First Post") {
        id
        title
      }
    }
  }
}

Here, a new user is created and a post is added for them at the same time; errors in either operation can be captured and returned in the response.

How Does GraphQL Work? 

If you are new to GraphQL, you might be wondering how the queries and mutations work behind the scenes using a central GraphQL schema. To help you understand better, let us break it down into 4 important steps, as mentioned in the above diagram. Each step plays an important role in how your data is requested and received:

1. The Query Resolution Process

When a query is sent to the GraphQL server, you are actually sending a request that looks like a list containing what you want. Given below are the steps for your reference:

1. Receive the Query: First, the server gets your request, which clearly says what information you’re asking for.

2. Validate the Query: After that, the server looks for your request to make sure it matches the rules that are defined in the schema. If you have requested something that does not exist or used the wrong type of data, the server will not run the query; it will simply send back an error to inform you of the issue.

3. Execute the Query: If your query is correct, the server focuses on the data you asked for. It checks each piece of information you requested and uses special functions, called resolvers, to find and return the right data from the database or other sources.

4. Return the Response: After getting all the required data and making the changes, the server then puts everything together in the same format as the original query and then sends it back to you.

2. The Role of Resolvers

Resolvers are really important in how GraphQL works. Every piece of data you ask for has a resolver behind it, which is basically a little function that knows where to get that data from or how to figure it out. If you don’t create your own resolver, GraphQL will use a default one that just looks for a matching field in the data it already has. But if you need to get data from somewhere more advanced, like a database or another service, you can create your own custom resolver to do that job for you.

3. Efficient Data Fetching

What makes GraphQL really smart is how it runs resolvers. Since you only ask for the data you need in your query, it only runs the resolvers for those specific fields. So, if you don’t ask for a user’s posts, it won’t bother running the posts resolver; this helps avoid extra work and saves time by skipping unnecessary database calls.

4. Handling Complex Queries

GraphQL is really good at handling complicated requests. For example, if you want to get a user’s posts and also the comments on each post, it can handle all of that in one neat request without any trouble. GraphQL handles each request step by step. This provides you with full control over how the data is collected and sent back, exactly the way you have asked. This helps to keep your API responses clean and simple. It also allows you to create very specific requests that match exactly the way you want to use the data in your application.

Advantages of GraphQL

1. Gets only what you need: You can only request what you want; nothing more or nothing less will be sent.

2. Fewer Requests: You can get all related data in a single query instead of making multiple calls.

3. Faster Apps: Since less data is being sent and received, your app will load quicker.

Disadvantages of GraphQL

1. Takes Time to Learn: GraphQL can be confusing at first if you are habituated to working with REST APIs.

2. Too much flexibility: It also provides clients with full control over their queries. This can result in generating requests that are overly complex.

3. Caching is Tricky: Since every request can be different, it is harder to cache responses in GraphQL when compared to REST.

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GraphQL vs REST API

Its is very important to understand the difference between GraphQL and REST API as it helps in choosing the right approach for fetching the data.

Conclusion

GraphQL provides you with a smarter way to work with APIs. Instead of working with multiple endpoints or dealing with unwanted data, it allows you to ask for exactly what you need. By learning how it works, from writing queries to creating resolvers, you will be able to understand the amount of control and flexibility it provides you. Whether you are building a small app or a complex system, it helps you manage your data efficiently. You might find it confusing at first, but once you understand, it can change the way you build applications.

If you want to learn more about APIs, explore our Top 50+ API Interview Questions blog and enroll in our Web Development Course. 

What is GraphQL – FAQs