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API DEVELOPMENT

A Comprehensive Guide to API Endpoints

Alicia Petit
June 6, 2024 | 29 min read
Guide to API Endpoints

APIs (application programming interface) have become the backbone of modern applications. APIs enable different software systems to communicate and exchange data seamlessly, making it possible to build complex and feature-rich applications by leveraging the functionality of various services and platforms.

At the heart of every API lies its endpoints–the specific URLs representing the entry points for accessing the API's resources and functionality. API endpoints define the contract between the API provider and the consumer, specifying the available operations, request formats, and response structures.

In this complete guide, we want to help you understand and how they work. We'll Show you how to build these endpoints within your organization and ensure they work effectively, efficiently, and securely. Let’s also explore howendpoints might change as technology progresses.

What is an API endpoint?

An API endpoint is a specific URL representing a resource or a collection of resources in an API. It is the entry point for an API request and where a client can access the API.

Here’s an example of a basic API endpoint:

GET /api/v1/users/{userId}

This endpoint represents a specific user resource identified by

{userId}
. It uses the GET HTTP method to retrieve the user's information. The response would typically include the user's details in a structured format like JSON:

{
"id": "123",
"firstName": "John",
"lastName": "Doe",
"email": "john.doe@example.com",
},
"createdAt": "2024-05-10T14:30:00Z",
}

This example shows a few key points about API endpoints:

  1. HTTP Methods: Each endpoint is associated with one or more HTTP methods (such as GET, POST, PUT, DELETE) that define the action to be performed on the resource. The example uses the GET HTTP method, indicating that the endpoint is used to retrieve information about a user resource.
  2. Resource Representation: Endpoints usually represent resources or entities in a system, such as users, products, or orders. The URL structure often reflects the hierarchical relationship between resources. The endpoint URL
    /api/v1/users/{userId}
    represents a specific user resource, where
    {userId}
    is a placeholder for the actual user identifier.
  3. Parameters: Endpoints can accept parameters to filter, sort, or specify the requested data. These parameters can be passed as query parameters in the URL or as part of the request body in POST or PUT requests. The
    {userId}
    in the endpoint URL acts as a parameter to specify the requested user resource.
  4. Response Format: The data returned by an endpoint is typically structured like JSON or XML, which can be easily parsed and processed by client applications.
  5. Versioning: API endpoints are often versioned to allow for backward compatibility and gradual updates. The version can be included in the URL (e.g.,
    /api/v1/users
    ) or specified through headers.

API endpoints form the contract between the API provider and the consumer, defining the available operations, required parameters, and expected responses. They provide a standardized way for client applications to interact with the API and access the desired functionality and data.

How API Endpoints Work

API endpoints provide a structured way for clients to interact with a server or service over a network. They act as the client's entry points to the server.

First, there is a client request. The client application sends an HTTP GET request to the API endpoint URL

/api/v1/users/{userId}
, where
{userId}
is replaced with the actual user identifier, such as "123". The request is sent to retrieve information about a specific user.

The server receives the incoming request and examines the URL (

/api/v1/users/{userId}
) and HTTP method (GET). Based on the defined API routes, the server determines that this request should be handled by the code responsible for retrieving a user resource. The server executes the code associated with the
/api/v1/users/{userId}
endpoint. It extracts the
userId
parameter from the URL, which in this example is "123". The code then retrieves the corresponding user data from the database or any other source based on the
userId
.

After retrieving the user data, the server generates an appropriate JSON response. In this example, the response includes the user's details such as

id, firstName, lastName, email,
and
createdAt
timestamp. The response typically has a status code 200 to indicate a successful request. The server sends the generated JSON response to the client over the network. The response includes the HTTP status code 200, headers (if any), and the JSON response body containing the user's details.

The client receives the JSON response from the server. It can examine the status code (200) to confirm the request's success. The client then parses the JSON data and extracts the relevant information, such as displaying the user's name and email on the user interface.

Some key concepts in how API endpoints work are:

  • API endpoints define the available operations, the expected request formats, and the structure of the responses. By adhering to the defined API contract, clients can effectively communicate with the server and perform desired actions or retrieve required data.
  • API endpoints are designed to be language-agnostic. The client and server can be implemented in different programming languages if they adhere to the defined API contract and communicate using standard protocols like HTTP and JSON/XML.
  • API endpoints provide a standardized and scalable way for different systems and web applications to integrate and exchange data, enabling seamless communication and functionality across multiple platforms and devices.

What is the difference between API resource and endpoint?

"API resource" and "API endpoint" are often used interchangeably. But there is a subtle difference between them:

  • An API resource represents a specific entity or concept within the API's domain. It is an abstraction of a real-world object or a business concept that the API exposes and manages. An example of an API resource is the "users" above, but it could also be "products," "orders," "articles," etc. Resources are typically named using nouns and follow a hierarchical structure, and each resource may have one or more associated endpoints that allow interaction with that resource.
  • An API endpoint is a specific URL that allows clients to interact with an API resource. It represents a specific operation or action that can be performed on a resource. They define the available HTTP methods (GET, POST, PUT, DELETE) and the corresponding request and response formats from above. Each endpoint is associated with a specific resource (or a collection of resources) used to create, read, update, or delete (CRUD) resources.

A resource is a conceptual entity within the API, while an endpoint is a concrete URL and HTTP method combination that allows interaction with that resource.

Here's an example to illustrate the difference:

Consider an API for managing blog posts. The API may have a resource called "posts" representing blog post entities. The "posts" resource can have multiple endpoints associated with it, such as:

  • GET /posts
    : Retrieves a collection of blog posts.
  • GET /posts/{id}
    : Retrieves a specific blog post by its ID.
  • POST /posts
    : Creates a new blog post.
  • PUT /posts/{id}
    : Updates an existing blog post.
  • DELETE /posts/{id}
    : Deletes a specific blog post.

In this example, "posts" is the API resource, and each URL and HTTP method combination (e.g., GET /posts, POST /posts) represents a different API endpoint for interacting with the "posts" resource.

Think of it this way: Endpoints are the actionable parts of an API that clients use to perform operations on resources, while resources are the conceptual entities that the API manages and exposes.

Types of API Endpoints

Let’s step up the complexity of API endpoints a little. So far, we’ve described REST (Representational State Transfer) endpoints, the most popular architectural style for designing web APIs. The endpoints are based on the HTTP protocol and use standard HTTP methods (GET, POST, PUT, DELETE) to perform operations on resources.

Two clear advantages of RESTful endpoints are:

  1. They are stateless, meaning each request contains all the necessary information to complete independently.
  2. They utilize URLs to represent resources and rely on HTTP status codes to indicate the outcome of the requests.

The main types of REST API endpoints are:

  • GET Endpoints: Used to retrieve resources or collections of resources. GET requests generally don't require a request body, and the parameters needed for the request are typically included in the URL as query parameters or path parameters.
  • POST Endpoints: Used to create new resources. The data for the new resource is sent in the request body. The request body contains the necessary information to make the resource, usually in JSON or XML format.
  • PUT Endpoints: Used to update existing resources with the updated data sent in the request body.
  • DELETE Endpoints: Used to delete resources. They may or may not require a request body. The resource to be deleted is usually specified in the URL itself, such as a path parameter.

While POST, PUT, and DELETE endpoints commonly require a request body to send data to the server for creating, updating, or deleting resources, GET endpoints typically don't require a request body because they are used for retrieving data. The necessary information is included in the URL.

However, it's worth noting that this is a general convention and not a strict rule. Sometimes, GET requests may include a request body, although it's less common and not widely used. The HTTP specification allows for a request body in GET requests, but it doesn't have any defined semantics and may be ignored by servers.

Here's an example of how you can use

fetch
in JavaScript to make asynchronous POST and DELETE requests:

const createUser = async (userData) => {
try {
const response = await fetch('/api/v1/users', {
method: 'POST',
headers: {
'Content-Type': 'application/json',
},
body: JSON.stringify(userData),
});
if (!response.ok) {
throw new Error('Failed to create user');
}
const createdUser = await response.json();
console.log('User created:', createdUser);
} catch (error) {
console.error('Error creating user:', error);
}
};
// Example usage
const newUserData = {
firstName: 'John',
lastName: 'Doe',
email: 'john.doe@example.com',
age: 30,
};
createUser(newUserData);

In this example, the

createUser
function takes
userData
as a parameter, which is an object containing the data for the new user. The function uses
fetch
to send a POST request to the
/api/v1/users
endpoint. The request includes a JSON body with the user data, which is stringified using
JSON.stringify()
.

Here’s the DELETE request:

const deleteUser = async (userId) => {
try {
const response = await fetch(/api/v1/users/${userId}, {
method: 'DELETE',
});
if (!response.ok) {
throw new Error('Failed to delete user');
}
console.log('User deleted successfully');
} catch (error) {
console.error('Error deleting user:', error);
}
};
// Example usage
const userIdToDelete = 123;
deleteUser(userIdToDelete);

In this example, the

deleteUser
function takes
userId
as a parameter, representing the ID of the user to be deleted. The function uses
fetch
to send a DELETE request to the
/api/v1/users/${userId}
endpoint, where
${userId}
is replaced with the actual user ID.
Then, there are a few other REST endpoints that are less used but useful in certain situations:

  • PATCH Endpoints: Used to partially update existing resources.
  • HEAD Endpoints: Used to retrieve metadata about a resource without returning the resource itself.
  • OPTIONS Endpoints: Used to retrieve information about the communication options available for a resource.

So far, so REST. But there are other types of API endpoints.

SOAP (Simple Object Access Protocol) is a protocol for exchanging structured information in web services. SOAP endpoints use XML (eXtensible Markup Language) for request and response formats, and they rely on the SOAP envelope structure, which includes a header and a body, to encapsulate the data.

SOAP endpoints typically use the POST HTTP method for all operations and define the action in the SOAP envelope.

POST /soap/getUserDetails
<?xml version="1.0"?>
<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope">
<soap:Header>
<Authentication>
<APIKey>your-api-key</APIKey>
</Authentication>
</soap:Header>
<soap:Body>
<GetUserDetails>
<UserId>123</UserId>
</GetUserDetails>
</soap:Body>
</soap:Envelope>

In this example, a SOAP request is sent to the

/soap/getUserDetails
endpoint. The request includes a SOAP envelope with a header containing authentication information (API key) and a body containing the
GetUserDetails
operation with the
UserId
parameter.

GraphQL is a query language and runtime for APIs that has grown in popularity over the past decade. GraphQL endpoints expose a single URL for all data retrieval and manipulation. Clients send queries or mutations to the GraphQL endpoint, specifying the desired data fields and operations. The server responds with the requested data in a structured format defined by the GraphQL schema.

POST /graphql
query {
user(id: "123") {
id
firstName
lastName
email
}
}

In this GraphQL example, a query is sent to the

/graphql
endpoint. The query specifies the desired data fields (
id, firstName, lastName, email
) for a user with a specific
id
. The server responds with the requested data in the specified format.

RPC (Remote Procedure Call) endpoints allow clients to invoke remote procedures or functions on the server. They abstract the communication details and provide a way to call server-side methods as if they were local functions. RPC endpoints can use various protocols, such as JSON-RPC, gRPC, or XML-RPC.

POST /rpc
{
"jsonrpc": "2.0",
"method": "calculateSum",
"params": [10, 20],
"id": 1
}

In this RPC example using JSON-RPC, a request is sent to the

/rpc
endpoint. The request includes the JSON-RPC version (
"jsonrpc": "2.0"
), the method to be invoked (
"method": "calculateSum"
), the parameters for the method (
"params": [10, 20]
), and a request ID (
"id": 1
). The server processes the request and sends back a response with the result.

Webhooks are a way for servers to send real-time notifications or data to clients. Clients register a webhook endpoint URL with the server, and the server sends HTTP POST requests to that URL whenever an event occurs or data becomes available. Webhooks are commonly used for event-driven architectures and for integrating different systems.

POST /webhook
{
"event": "new_user_registered",
"data": {
"userId": "123",
"email": "john.doe@example.com"
}
}

In this webhook example, the server sends an HTTP POST request to the registered webhook URL (

/webhook
) whenever a specific event occurs. The request body includes the event type (
"event": "new_user_registered"
) and the associated data (
"data": { ... }
). The client receiving the webhook can then process the event and perform necessary actions.

Each type of API endpoint has its characteristics and use cases. The choice of endpoint type depends on factors such as the architecture style, communication protocol, data format, and the API's and its clients' specific requirements.

It's important to note that these endpoint types are not mutually exclusive, and an API can utilize multiple types of endpoints depending on its needs and design choices.

Security in API Endpoints

Security is a crucial aspect of designing and implementing API endpoints. Without securing your API endpoints, you risk exposing sensitive data, allowing unauthorized access, and potentially compromising the entire system. Attackers could exploit vulnerabilities to steal information, perform malicious actions, or disrupt the service.

The most basic security strategy for API endpoints is authentication and authorization. Authentication verifies the client's identity before making the API request, while authorization determines what actions or resources the authenticated client is allowed to access.

Authentication in APIs is commonly achieved through tokens or API keys. When clients authenticate with the API, they are issued a unique token or key that must be included in subsequent API requests. The server verifies the validity of the token or key before processing the request, ensuring that only authenticated clients can interact with the API.

One popular authentication mechanism is JSON Web Tokens (JWT). JWTs are compact, self-contained tokens consisting of a header, payload, and signature. The header contains metadata about the token, the payload contains claims (such as user information), and the signature verifies the integrity of the token. JWTs are often used with OAuth 2.0, an authorization framework that enables secure delegated access to API resources.

Here's an example of how JWT authentication can be implemented in an API endpoint:

  1. The client sends a POST request to the
    /api/v1/login
    endpoint with their credentials (e.g., username and password) in the request body.
  2. If the credentials are valid, the server generates a JWT containing the user's information and a secret key known only to the server.
  3. The server sends the JWT back to the client in the response body.
  4. For subsequent API requests, the client includes the JWT in the
    Authorization
    header of the request.
  5. The server verifies the JWT's signature using the secret key and extracts the user information from the token's payload.

If the JWT is valid, the server processes the request and returns the appropriate response.

Authorization, on the other hand, determines what actions or resources an authenticated client is allowed to access. Role-based access control (RBAC) is a common approach to implementing authorization in APIs. With RBAC, each user is assigned one or more roles, and each role is associated with a set of permissions. The API server checks the user's role and permissions before allowing or denying access to specific endpoints or resources.

For example, consider an API with two roles: "admin" and "user." The "admin" role may have permissions to perform all CRUD (Create, Read, Update, Delete) operations on a resource, while the "user" role may only have permissions to read and update their data. The API server would enforce these permissions based on the user's role when handling requests.

In addition to authentication and authorization, rate limiting is another crucial security measure for API endpoints. Rate limiting involves restricting the number of requests a client can make to the API within a specific time window. This helps prevent abuse, protects against denial-of-service (DoS) attacks, and ensures fair usage of API resources.

Rate limiting can be implemented using various strategies, such as:

  • Throttling: Limiting the number of requests a client can make per second, minute, or hour. Once the limit is reached, subsequent requests are rejected until the next time window.
  • Quota-based limiting: Assigning a fixed quota of requests to each client for a given period (e.g., 1000 requests per day). Once the quota is exhausted, further requests are blocked.
  • IP-based limiting: Tracking and limiting requests based on the client's IP address to prevent a single client from overwhelming the API.

Rate limiting is typically enforced by the API server or an API gateway in front of the API. When a client exceeds the rate limit, the server responds with an appropriate HTTP status code (e.g., 429 Too Many Requests). It may include headers indicating the remaining limit or the time until the limit resets.

Here is how you can set your API gateway to limit access to the IP address of a user:

apiVersion: getambassador.io/v3alpha1
kind: Mapping
metadata:
name: quote-backend
spec:
hostname: "*"
prefix: /backend/
service: quote
labels:
ambassador:
- request_label_group:
- remote_address:
key: remote_address

remote_address
is the IP address we want to limit, and we then use this Mapping in a rate limit service to limit each IP address to 3 requests per minute:

apiVersion: getambassador.io/v3alpha1
kind: RateLimit
metadata:
name: backend-rate-limit
spec:
domain: ambassador
limits:
- pattern: [{remote_address: "*"}]
rate: 3
unit: minute

Implementing rate limiting helps protect your API from abuse, ensures fair usage among clients, and maintains the stability and performance of your API infrastructure.

Remember, security is an ongoing process requiring continuous monitoring, updating, and improvement. Review and assess security measures regularly, stay informed about the latest security threats and vulnerabilities, and adapt security strategies accordingly.

10 Best Practices for Designing API Endpoints

When designing API endpoints, following best practices can lead to a well-structured, maintainable, and developer-friendly API. Here are some essential best practices for designing API endpoints:

  1. Use RESTful Principles: When designing your API endpoints, follow RESTful principles by using HTTP methods (GET, POST, PUT, DELETE) to represent operations on resources. Then, use meaningful and descriptive resource names and URLs to represent entities and their relationships. Utilize HTTP status codes to indicate the outcome of API requests.
  2. Consistency and Naming Conventions: Maintain consistency in the naming conventions used for endpoints, parameters, and response fields. Use clear, descriptive, and self-explanatory names for resources and endpoints. Follow a consistent case style (e.g., snake_case or camelCase) throughout the API and use plural nouns for collections and singular nouns for individual resources.
  3. Versioning: Include versioning in your API endpoints to manage changes and maintain backward compatibility. Use a version prefix in the URL (e.g., /v1/users) or include a version parameter in the request header and communicate the versioning strategy in the API documentation.
  4. Pagination: Implement pagination for endpoints that return large datasets. Use query parameters to control the pagination behavior, such as page number and page size. Include pagination metadata in the response, such as total count, current page, and links to previous/next pages.
  5. Error Handling: Provide meaningful and consistent error responses when something goes wrong. Use appropriate HTTP status codes to indicate the type of error (e.g., 400 for bad request, 404 for not found). Include error details in the response body, such as an error code, message, and additional context. Maintain a consistent error response format across all endpoints.
  6. Documentation: Provide clear and comprehensive documentation for your API endpoints. Include details about endpoint URLs, HTTP methods, request/response formats, authentication requirements, and error handling. Use tools like OpenAPI to generate interactive and up-to-date API documentation. Provide code examples and SDKs to help developers get started quickly.
  7. Response Formats: Choose a consistent and widely supported response format, likely JSON. Use a consistent structure for response payloads across all endpoints. Include relevant metadata, such as timestamps, pagination information, or links to related resources. Consider using envelopes or wrappers to provide additional context or metadata.
  8. Caching: Implement caching mechanisms to improve performance and reduce server load. Use appropriate HTTP caching headers like Cache-Control and ETag to control caching behavior. Provide guidance in your API documentation on how clients should handle caching.
  9. Rate Limiting and Throttling: Implement rate limiting and throttling to protect your API from abuse and ensure fair usage. Set appropriate rate limits based on the client's subscription or usage tier and provide clear error responses and headers to indicate when rate limits are exceeded.
  10. Monitoring and Analytics: Implement monitoring and analytics to gain insights into API usage and performance. Track metrics like response times, error rates, and popular endpoints and use logging and monitoring tools to detect and troubleshoot issues proactively.

These best practices serve as guidelines, and the specific design decisions may vary depending on your API's requirements, audience, and ecosystem. When designing your API endpoints, it's important to consider the needs of your API consumers and strike a balance between simplicity, flexibility, and robustness.

Future Trends in API Endpoints

As technology evolves and new requirements emerge, API endpoints undergo advancements and innovations.

Serverless APIs

Serverless architecture is becoming increasingly popular for building and deploying APIs, leveraging cloud platforms like AWS Lambda, Azure Functions, or Google Cloud Functions

Serverless APIs allow developers to focus on writing code without worrying about infrastructure management. They enable automatic scaling, pay-per-use pricing, and simplified deployment and management.

With serverless APIs, developers can build and deploy APIs more quickly and cost-effectively as the cloud provider handles the underlying infrastructure and scaling.

Asynchronous APIs

Asynchronous APIs are also gaining traction for handling long-running or resource-intensive tasks. They allow clients to initiate a request and receive an immediate response while processing happens in the background.

Asynchronous APIs use webhooks or message queues to notify clients when the task is completed, providing better performance, scalability, and improved user experience for complex operations. These APIs are particularly useful for tasks that require significant processing time, such as video encoding, data analysis, or batch operations.

API-First Development

API-first development approaches are gaining prominence. These approaches prioritize the design and development of APIs before building the user interface or other components. This approach ensures that APIs are well-designed and consistent and meet the needs of multiple clients and platforms. API-first development promotes reusability, modularity, and faster development cycles, enabling the creation of ecosystem-driven applications and encouraging collaboration between teams.

By focusing on APIs first, organizations can create more flexible and interoperable systems that integrate easily with other services and platforms.

AI/ML Integration:

The integration of AI and machine learning (ML) capabilities into APIs has been a growing trend since the launch of advanced LLMs. AI-powered APIs can provide intelligent recommendations, personalized experiences, and automated decision-making. ML models can be exposed through APIs, allowing clients to leverage pre-trained models for tasks like image recognition, natural language processing, or predictive analytics. By incorporating AI and ML into APIs, developers can build more innovative and intelligent applications, enhancing the value and capabilities of their services.

API Composition

Finally, API composition and microservices architecture transform how APIs are designed and deployed. API composition involves building new APIs by combining and orchestrating existing APIs, while microservices promote the development of small, focused, and independently deployable services, each with its API.

This approach enables the creation of flexible and scalable systems by leveraging existing APIs as building blocks. It allows for faster development, easier maintenance, and the ability to evolve individual services independently. API composition and microservices promote the reuse and integration of existing APIs, enabling the creation of complex and feature-rich web applications by combining specialized services.

These future trends in API endpoints reflect the ongoing evolution of API design and development practices. As technology advances and new requirements arise, API design and development practices will continue to evolve to meet the changing needs of developers and users alike. Adopting these trends can help organizations build more efficient, scalable, and future-proof APIs that deliver value to their consumers. Staying updated with the latest trends, best practices, and industry standards is important to build modern, efficient, and future-proof APIs.