What Is GraphQL? How Does It Differ from REST APIs?

GraphQL is an API query language that allows clients to retrieve the data they need by querying it. In this guide, we will explore what GraphQL is, how it works, its key features and advantages, and the differences between GraphQL and REST APIs.

What is GraphQL?

GraphQL is a query language and runtime approach used to retrieve data from APIs and perform operations on that data. The client can specify the fields it needs within a query and request the corresponding data from the server.

GraphQL was released as open source by Facebook in 2015. Today, it can be used with different programming languages and technologies.

GraphQL APIs have a schema that defines the data structure provided by the API. This schema determines which data types and operations clients can use.

How does GraphQL work?

In an application that uses GraphQL, the client sends a query to the server. The query explicitly specifies which data is needed.

For example, if an application needs to display a user's name, email address, and orders, these fields can be requested within the same query. The server evaluates the query according to the GraphQL schema and returns the requested data.

This structure can reduce the amount of unnecessary data received by the client. It can also allow related data to be retrieved through a single query.

What are the key features of GraphQL?

To understand how GraphQL works, it is important to look at how queries are structured and how the API's data model is defined. GraphQL manages data exchange between the client and server through more clearly defined rules.

• Schema-based structure: The data types and operations supported by the API are defined through a schema.
• Client-driven data selection: The client can specify the fields it needs in its query.
• Single endpoint: GraphQL APIs typically use a single endpoint to which queries are sent.
• Nested data queries: Related data can be requested within a single query.
• Type system: Data types are explicitly defined in the schema.
• Query validation: Submitted queries can be checked against the schema rules before execution.

What are Query, Mutation, and Subscription in GraphQL?

In GraphQL, the operations performed by the client are primarily represented by the concepts of Query, Mutation, and Subscription. Each of these structures serves a different purpose.

A Query is used to retrieve data from the server. A Mutation is used to perform changes such as creating, updating, or deleting data. A Subscription, when supported by the system, can enable data changes to be delivered to the client in real time.

This distinction helps model operations performed through the API in a more structured and understandable way.

What are the advantages of GraphQL?

One of the key features of GraphQL is that it allows the client to explicitly specify the data it needs. This approach can be particularly useful in applications where different screens have different data requirements.

• Can reduce unnecessary data transfer: The client can request only the fields it needs.
• Can reduce multiple requests: Related data can be retrieved through a single query when the schema is appropriately designed.
• Provides type safety: Data types defined in the schema help create queries in a more controlled way.
• Can simplify API development: New fields can be added to the schema while existing queries can remain compatible.
• Can adapt to different clients: Web, mobile, or other applications can create queries based on their individual data requirements.

What are the disadvantages of GraphQL?

Although GraphQL provides a flexible data querying structure, it may not be equally suitable for every project. Some additional considerations need to be managed when designing and operating a GraphQL API.

As query complexity increases, monitoring server-side resource usage and performance can become more important. In addition, appropriate designs may be required for areas such as caching, authorization, error handling, and query complexity control.

Therefore, when using GraphQL, it is important to consider not only the convenience it provides to clients when retrieving data but also the operational requirements on the server side.

What is a REST API?

A REST API is a widely used API approach that enables applications to communicate with each other over HTTP and is based on performing operations on resources.

In a REST architecture, resources such as users, products, or orders can be represented through different URLs. For example, one endpoint can be used to retrieve products, while another endpoint can be used to retrieve a specific product.

REST APIs commonly use HTTP methods such as GET, POST, PUT, PATCH, and DELETE. The returned data is often provided in JSON format.

What are the differences between GraphQL and REST APIs?

GraphQL and REST can both be used for data exchange between clients and servers. However, they differ in how data is requested and how APIs are structured.

These differences do not mean that one technology is always more suitable than the other. The requirements of the API, data structure, and preferences of the development team can all influence the choice.

Should you use GraphQL or a REST API?

The choice between GraphQL and REST should be evaluated based on the project's requirements. If clients have different data needs and related data needs to be queried flexibly, GraphQL may be considered.

REST APIs may be preferred for applications with simpler resource structures or systems that aim to make extensive use of HTTP standards. Existing infrastructure, team experience, performance requirements, and the way the API will be used should also be taken into consideration during the decision-making process.

What types of projects use GraphQL?

GraphQL can be used in applications where different clients have different data requirements while accessing the same API. A web application and a mobile application accessing the same data sources with different sets of fields can be an example.

GraphQL's querying structure can be particularly useful in systems where retrieving related data together is important. However, as the complexity of the API increases, areas such as schema management, authorization, and performance also need to be planned carefully.

GraphQL is a flexible API approach that allows clients to query the data they need. REST APIs, on the other hand, are a widely used alternative built around resources and HTTP methods. The choice between the two approaches should be based on the project's data structure, client requirements, and technical needs.