What is GraphQL?

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. If that’s so, then you are in the right place.
In this blog, we are going to talk about what GraphQL is, how it works, its key features, and how it is different from other REST APIs. So let’s get started.

Table of Contents:

• What is GraphQL?
  • Key Features of GraphQL
• Key Components of GraphQL
  1. Schema
  2. Query
  3. Mutation
  4. Subscription
  5. Resolvers
  6. Types
  7. Fields and Arguments
  8. Directives
• How Does GraphQL Work?
  1. The Query Resolution Process
  2. The Role of Resolvers
  3. Efficient Data Fetching
  4. Handling Complex Queries
• Advantages of GraphQL
• Disadvantages of GraphQL
• Conclusion

What is GraphQL?

GraphQL is basically a query language for APIs and a runtime for fulfilling those queries with your existing data. 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

GraphQL consists of some important features that make it different from traditional REST APIs. These features provide you with more control and make it easier for you to work with data. Let us have a look at them below:

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: GraphQL 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: GraphQL 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: GraphQL uses only a single URL rather than making separate calls to separate sets of data, like in REST, although you do need a GraphQL 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. Send Multiple Queries Together: 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.

7. Great for Mobile Apps: Since GraphQL only sends the data that you ask for, it uses less internet and works better on mobile devices.

8. No Need for API versions: When you make changes to your API, GraphQL allows you to update the API without making a new version or making the old apps that still use that API.

Key Components of GraphQL

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

1. Schema

The Schema is basically the backbone of any GraphQL API. It is used to define the kind of data that you can ask for and how you can structure that data. You can think of GraphQL as a plan or blueprint that helps the front end and the backend collaborate with each other. It lists what kind of data is available, like users, products, posts, and what details each of these data points has. It also displays how the different types of data are connected to each other. Every piece of data in the schema has a specific type, like text (String), number (Int), or true/false (Boolean), so that everything stays organized and free from errors.

2. Query

In GraphQL, a query is basically how you ask the server for 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 asked for. This helps to keep things clean and efficient.

Example:

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

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

3. Mutation

In GraphQL, while queries are used to fetch data, you can use mutations when you want to change the data. 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 some input and then return the result after the change is made. This helps you to see what was added or updated.

Example:

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

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

4. Subscription

Subscriptions in GraphQL are used to set up real-time communication between the client and the server. This means that when anything changes on the server, like a new message, update, or event, the client gets updated about that change automatically. This can be useful for live features like chat applications, notifications, or real-time dashboards where you want the data to be updated instantly.

5. Resolvers

Resolvers in GraphQL are components that work behind the scenes. They know how to get the actual data you want. When you send a query or a mutation, GraphQL checks the schema to understand what you want and then calls the resolver functions to fetch that data, whether it is from a database, another API, or somewhere else. You can assume resolvers to be the logic that connects your data to the right data source and then returns the correct information. 

6. Types

In GraphQL, types are used to define the shape and structure of your data in the schema. They help describe what kind of data can be sent or received. There are different kinds of types. Scalar types are the basic ones, like String for text, Int for numbers, Float for decimals, Boolean for true/false, and ID for unique identifiers. Then you have object types, which are custom types that group related fields together—for example, a User type might include fields like name, email, and age. There are also input types, which are used when you’re sending data into the system, such as when you’re creating or updating something using a mutation.

7. Fields and Arguments

In GraphQL, fields are the specific pieces of data that you want to get or change, like a person’s name, email, or price of a product. When you write a query or mutation, you have to list the fields that you need. Along with those fields, you can also use arguments in order to filter or narrow down your request. For example, if you want to get information about a specific user, you use the ID as an argument to get the information about that user. This helps to make your requests more accurate.

Example:

{
  product(id: "101") {
    name
    price
  }
}

The above GraphQL query requests the name and price of the product with the ID “101”.

8. Directives

In GraphQL, directives help you to change the way your queries or schemas behave based on some conditions. They provide you with more flexibility by allowing you to include or skip some specific fields when required. Two common directives are: @include and @skip. These 2 directives help you to decide whether you need to show or hide the parts of your query. This can be useful when you want your queries to adjust depending on different situations.

How Does GraphQL Work? 

If you are new to GraphQL, you might be wondering how it works behind the scenes. 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 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 GraphQL schema. If you’ve asked for something that doesn’t exist or used the wrong type of data, the server won’t run the query; it will just send back an error to let you know what’s wrong.

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, GraphQL 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, GraphQL 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.

As you get more comfortable writing queries and setting up resolvers, you’ll see that GraphQL gives you a strong and flexible way to build apps that are fast, smart, and give you exactly the data you need.

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.

4. Strongly Typed: It defines the data types clearly. This helps you to identify your mistakes clearly.

5. Easy to Evolve: You can add the new fields without breaking any existing apps. Therefore, there is no need for versioning.

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: GraphQL 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.

4. Needs Proper Planning: You have to design your schema and resolvers carefully. Otherwise, things can get confusing for you.

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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 GraphQL 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, GraphQL 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. 

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