Understanding API Types: SOAP, REST and GraphQL
When working with any systems, APIs are one of the most important building blocks. They define how different parts of an application communicate, whether it's between a frontend and a backend, or between entirely different applications.
There are several ways to design an API, and among the most common approaches are SOAP, REST and GraphQL. Although they all enable communication, they differ significantly in how they structure requests, handle data, and solve specific problems.
Understanding these differences helps you choose the right approach for each scenario and for your application.
SOAP (Simple Object Access Protocol)
SOAP is a protocol designed for systems that require a high level of reliability and strict communication rules.
It uses XML as its format and relies on well-defined contracts (WSDL), which clearly specify how requests and responses should be structured.
A simple SOAP request looks like this:
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<GetUserRequest>
<id>8</id>
</GetUserRequest>
</soap:Body>
</soap:Envelope>
And the response:
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<GetUserResponse>
<name>Leonardo</name>
<email>leosmsilvx@gmail.com</email>
</GetUserResponse>
</soap:Body>
</soap:Envelope>
Because of its strictness, SOAP is commonly used in enterprise environments, especially where security, consistency, and formal contracts are essential. On the other hand, its verbosity and complexity make it less common in modern web applications or simple ones.
REST (Representational State Transfer)
REST is currently the most widely used architectural style for APIs.
It is based on simple principles, resources are identified by URLs, standard HTTP methods are used (GET, POST, PUT, DELETE) and data is typically exchanged in JSON.
A basic REST request might look like this:
GET /users/8 HTTP/1.1
With a response like:
{
"id": 8,
"name": "Leonardo",
"roles": ["admin", "editor"]
}
REST is popular because it is intuitive and works well for many use cases. However, as applications grow in complexity, it can lead to challenges such as making multiple requests to gather related data or receiving more data than necessary.
Even so, for many systems, REST remains a practical and efficient choice.
GraphQL
GraphQL was introduced to address some of the limitations found in REST, particularly around data fetching.
Instead of multiple endpoints, GraphQL exposes a single endpoint where the client specifies exactly what data it needs.
For example:
query GetUser {
user(id: 8) {
id
name
posts {
title
}
}
}
Response:
{
"data": {
"user": {
"id": 8,
"name": "Leonardo",
"posts": [
{ "title": "Minimalism is not synonymous with good design" }
]
}
}
}
This approach reduces unnecessary data transfer and can simplify data fetching for complex interfaces. However, it introduces additional complexity on the server side, requiring careful handling of queries, performance, and security.
GraphQL is especially useful when different clients need different subsets of data or when relationships between entities are more complex.
Choosing between approaches
Each of these API styles is designed with different goals in mind:
- SOAP focuses on strict contracts and reliability
- REST emphasizes simplicity and standardization
- GraphQL provides flexibility in data retrieval
Rather than thinking in terms of which one is “better,” it is more useful to consider the specific needs of your application.
Conclusion
APIs are not just about enabling communication, they shape how systems evolve over time.
Choosing between SOAP, REST, GraphQL or even WebSockets (article coming soon) is less about preference and more about understanding trade-offs. Each approach offers advantages in certain contexts and challenges in others.
Don’t choose an API because it’s popular, choose it because it fits your problem.