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Published on: September 24, 2025

{  
  "name": "John Doe",  
  "email": "john.doe@example.com"  
}

https://api.example.com/users?status=active&page=2

API endpoints follow a systematic flow, ensuring data is accurately exchanged between clients ( apps or web browsers) and servers.

Let's break down into the following steps:

• Client Sends a Request: When you interact with an app to perform a specific action, it sends a HTTP request to a specific endpoint. This request could be a GET (to fetch data), POST (to send new data), PUT (to update existing data), or DELETE (to remove data), depending upon the specific operation to perform.

  Along with this, the request might include extra information like headers, parameters, or even a body, depending on the operation.

  Example: Imagine you're using a mobile banking app to check your account balance. When you tap on “Check Balance”, the app sends a GET request to the bank’s server, like: GET /account/{account_id}/balance

• Server Validates the Request: Once the request reaches the server, it first checks if everything is in order. The server checks whether the request is correctly formatted and verifies any required authentication like an API key or OAuth token. If something’s missing, incorrect, or unauthorized, the server will send back an error response, such as 401 Unauthorized or 400 Bad Request.

  Example:The server checks if you’re logged in and if your account details are correct. If you haven’t logged in or if your session has expired, the server will respond with a 401 Unauthorized error.

• Server Processes Logic: Once your request is validated, the server performs the requested action, which can be fetching data, updating information, or triggering an action as per the HTTP request.

  Example: Once the server checks and confirms that your account login is valid, it retrieves your account details. It fetches your current balance from the database. Before giving the final amount, it might also check if there are any pending transactions that could impact your current balance, like recent withdrawals or deposits that haven nott cleared yet.

• Server Sends a Response: Finally, the server sends back a response to the client in a structured format (JSON is the most commonly used format), along with an HTTP status code. If the request was successful, the server will return a 200 OK status.

  However, if there is an issue with the request, you might receive an error based on the type of issue. If it shows 404 Not Found, this means that the requested resource does not exist. But if it shows 500 Internal Server Error, this indicates that something went wrong on the server side. Example: Finally, the server sends back a response like this:

  {  
    "account_id": "12345",  
    "balance": "500.75 USD",  
    "status": "success"  
  }

  Here, the balance shows the amount in your account, and the status confirms that the request was successfully processed.

API endpoint are important for the following reasons:

• Efficient Communication: API endpoints provide a standardized way for applications to communicate with each other. They ensure that data requests and responses are handled systematically, which helps systems work seamlessly together.

  Without them, your application cannot interact with external services like payment gateways, weather services, or login providers.

• Support Integration and Scalability: Well-structured API endpoints make it easy to expand your application. Suppose a developer wants to add a new feature to the application, like a payment gateway or an AI-powered chat assistant, then he doesn’t need to rebuild the entire system. He can just connect the new feature to the right endpoint.

  This modular approach is great for microservices. As user traffic grows, you can scale specific parts of the system that need more resources, while keeping everything running smoothly and efficiently.

• Security: Properly secured API endpoints are vital for protecting sensitive data. With techniques like token authentication and secure headers, endpoints help ensure that only authorized users can access certain resources.

• Improve Testing and Monitoring: Clear and structured API endpoints make it easier to pinpoint issues when something goes wrong. By using standard HTTP status codes and response structures, developers can quickly identify and address problems.

  Since every endpoint is a defined access point, QA engineers can validate responses, monitor uptime, and ensure reliability through automated API tests.

There are different types of API endpoints based on the specific needs of the application and the type of data exchange required to perform the operation.

The most common types of API endpoints are listed below with a relevant example to demonstrates how they function:

1. RESTful Endpoints

RESTful API endpoints use standard HTTP methods like GET, POST, PUT, and DELETE to perform operations on resources. They are stateless, meaning each request carries all the information required without relying on past interactions. This makes them simple, scalable, and widely used in software testing platforms.

Example:

To create a new user on a platform, you might use the following:

POST /api/users

This sends the data required to create a user, such as their name and email address.

2. GraphQL Endpoints

GraphQL allows clients to specify exactly what data they need, which minimizes unnecessary data transfer. Instead of multiple API calls, a single query can request data from different sources at once, making it more efficient for applications that need dynamic queries.

Example:

Suppose you are building an e-commerce website, and you need to display product list. Each product has a name, price, and image. Instead of fetching all the data for each product, which includes descriptions, reviews, or inventory levels, you can use GraphQL to request only the specific data you need:

{

  products {

    name

    price

    image

  }

}

This GraphQL query will return only the name, price, and image of each product, making your website more efficient by reducing the amount of data transferred. This approach is used for scenarios where you want to reduce the data load, improve performance and speed, especially when dealing with large catalogs or inventory systems.

3. SOAP Endpoints

SOAP (Simple Object Access Protocol) is a protocol used for exchanging structured information between systems over a network. Unlike REST, which uses lightweight data formats like JSON, SOAP relies on XML to send messages.

SOAP endpoints are typically used in systems that require strict security, reliability, and a standardized message format. These endpoints are well-suited for complex operations where security and transactional reliability are critical, such as in banking, insurance, and enterprise applications.

A key feature of SOAP endpoints is their use of envelopes to wrap the message. The envelope contains a header and a body: the header provides metadata, while the body contains the actual request or response. This structured approach makes SOAP well-suited for operations requiring multiple steps or validation.

Example:

Imagine you're working on an enterprise application that processes insurance claims. To retrieve the status of a claim from the server, you can use a SOAP request. The request would look like this:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ins="http://example.com/insurance">

   <soapenv:Header/>

   <soapenv:Body>

      <ins:GetClaimStatus>

         <ins:claimID>12345</ins:claimID>

      </ins:GetClaimStatus>

   </soapenv:Body>

</soapenv:Envelope>

In this example, Envelope is the XML wrapper that contains both Header and Body. The header basically contains metadata like authentication details or routing instructions, while the body holds the actual request. In this example, it was requesting for the status of a specific insurance claim (12345).

SOAP structure facilitates secure and reliable communication, making it ideal for applications where data integrity and security are a top priority, such as financial services, insurance, or healthcare systems.

4. WebSocket Endpoints

WebSocket endpoints enable real-time, full-duplex communication between the server and client. They are ideal for applications requiring constant data updates, like chat apps or live sports feeds.

Example:

A WebSocket endpoint for receiving live stock price updates could be:

wss: //api.stockexchange.com/real-time-updates

By keeping the WebSocket connection open, the server can push real-time updates to the client whenever new stock data is available.

Type	Protocol Used	Data Transmission	Key Use Cases
RESTful	HTTP/HTTPS	Stateless CRUD operations	Recommended for scalable and flexible systems where you need to manage data with CRUD operations like create, read, update, and delete. This is ideal for web and mobile apps that require efficient data management with easy integration and scalability.
GraphQL	HTTP/HTTPS	Client-specified queries	Great for apps that need to fetch only the required data. Recommended for dashboards and real-time applications, where you want to minimize data load and improve performance.
SOAP	XML over HTTP	Rigid, structured messages	Best for secure, enterprise-level systems that require high data integrity, such as banking, insurance, and healthcare applications, where reliable, secure data exchange is essential.
WebSocket	WebSocket protocol	Full-duplex, real-time updates	Recommended for real-time apps like live chat, stock feeds, or instant notifications, where low-latency communication between server and client is critical.

Why Test API Endpoints?

Because APIs are your system’s contract. Testing endpoints verifies functionality, prevents contract drift, secures auth paths, protects integration points, and catches performance and compatibility issues before they hit users or downstream services.

Testing API endpoints prevents many common issues, such as data errors, security gaps, and performance bottlenecks. Here is how effective tests help mitigate risks:

• Contract & schema drift: API documentation like OpenAPI should be the single source of truth. Tests validate if the API endpoints follow the documented contract. Any discrepancies between the spec and actual response are caught early, ensuring the system doesn't break during updates.
• Backward compatibility: API versioning is crucial. With proper endpoint testing, you can ensure that old versions of the API still work as expected even when new versions are released.
• Data correctness: Endpoints should be tested to validate that data returned in responses conforms to expected types, ranges, and formats. For example, you wouldn’t want a price field to return a negative number or a date field in an incorrect format.
• AuthN/AuthZ gaps: Testing endpoint authentication ensures that only authorized users or services can access specific resources. It verifies correct scopes and permissions are assigned.
• Performance regressions: As the API evolves, endpoint testing helps detect performance issues, such as slower response times or increased error rates, especially when the load increases.
• Resilience: Test idempotency and retry behavior across distributed systems. For instance, if a request fails, it should either return the same response or properly handle retries.
• Observability: Make sure the API server adds enough details in error messages, such as structured error bodies and correlation IDs, to make debugging easy.

However, manual API testing can be time-consuming and error-prone. With LambdaTest KaneAI, a GenAI-native testing agent, you can automate the process of API testing, making it smarter, faster, and more efficient. By leveraging AI, KaneAI simplifies the validation of API functionality, security, and performance, all while significantly reducing testing time.

Testing API endpoints is a crucial step in ensuring that your application's backend works as intended. Effective testing helps identify issues early and ensures that the API performs reliably under different conditions.

When testing API endpoints, you should focus on the following areas:

1. Functional Testing

This ensures that the API performs the expected functions under normal conditions. For example, sending a POST request to an API should return the expected result based on the input provided.

Example: If you're testing a payment processing API, send sample payment data and validate that it processes the transaction correctly, updating the status to “completed.”

2. Security Testing

API security testing ensures that your endpoints are protected against unauthorized access and potential vulnerabilities. This includes validating authentication mechanisms, like OAuth or API tokens, and ensuring that sensitive data is encrypted.

Example: Test your authentication API endpoint to ensure that only authorized API clients can access the protected resources. This includes testing different authentication methods like JWT (JSON Web Tokens).

3. Load Testing

It’s very important to ensure that your API can handle the expected load and scale when under stress. This includes testing with large numbers of simultaneous requests to see how the system responds.

Example: Simulate hundreds or thousands of API requests in parallel to ensure that the API server can handle high traffic without slowing down or crashing.

4. Error Handling Testing

Test how the API handles invalid or unexpected inputs. For instance, ensure that the API returns appropriate error codes and messages when it encounters problems, like an invalid API key or missing parameters.

Example: If a GET request is made to a nonexistent endpoint, ensure that the response code is 404 (Not Found) and the response body includes an appropriate error message.

5. Integration Testing

Test how the API interacts with other services. This could involve calling other APIs or integrating with databases to ensure everything works together as expected.

Example: Test an API endpoint that fetches data from a database. Ensure that the API returns accurate results, handles timeouts gracefully, and provides proper error responses when the database is down.

6. Response Time Testing

Testing the response time of your API is important to ensure that your users don't experience delays. A typical response time for an API should be less than 200ms, depending on the complexity of the request.

Example: If you’re testing a payment gateway API, ensure that the response time does not exceed 200ms during peak hours.

API testing is a vital practice for ensuring APIs are functional, secure, and efficient. Here are four of the most widely used API testing tools:

1. Postman

Key Features:

• Automated Testing: Easily automate tests using Postman’s Collection Runner to execute API tests in sequence.
• Request Building: Quickly build API requests with support for complex query parameters, headers, and authentication.
• Integration: Integrates seamlessly with CI/CD pipelines for automated testing in your build process.

Use Case: Postman is an excellent tool for developers and testers who need quick and reliable API testing. It's ideal for debugging API responses, running automated tests, and generating detailed reports.

2. Swagger

Key Features:

• API Documentation: Automatically generates interactive API documentation, making it easier for teams to understand API endpoints and functionality.
• Automated Testing: Leverage SwaggerHub for automated API testing directly from the documentation.
• Mock API: Create mock APIs to simulate real-world scenarios and test API behavior without backend dependency.

Use Case: Swagger is widely used for designing, documenting, and testing APIs. It’s perfect for teams looking to integrate API documentation with testing for better collaboration.

3. SoapUI

Key Features:

• Comprehensive Testing: Supports both REST and SOAP web services, ensuring robust testing for diverse APIs.
• Security Testing: Built-in security testing features to help identify vulnerabilities and ensure your API is safe from attacks.
• Data-Driven Testing: Facilitates testing with multiple data sets to verify API responses under various conditions.

Use Case: SoapUI is favored by large enterprises or teams dealing with legacy systems or needing to test complex SOAP services. It’s ideal for comprehensive testing, including security and data-driven scenarios.

4. Insomnia

Key Features:

• User-Friendly Interface: Provides an intuitive interface for creating and testing HTTP requests with full support for REST, GraphQL, and WebSocket APIs.
• Environment Variables: Supports environment variables to streamline testing across different setups and servers.
• Advanced Authentication: Insomnia offers built-in support for various authentication mechanisms, including OAuth 2.0 and JWT tokens.

Use Case: Insomnia is perfect for developers looking for a lightweight, intuitive tool for API testing. It’s especially useful for teams needing flexibility in testing multiple types of APIs without a steep learning curve.

Testing happens before release, but once your API is live, monitoring is key. It ensures your endpoints stay healthy, respond quickly, and don’t break under real-world usage.

You can use Prometheus & Grafana for tracking API health. These two tools work together to give real-time insights into your API performance.

How to Use Them:

1. Prometheus: Collects metrics such as request count, error rate, and response times.

2. Grafana: Visualizes this data on dashboards and lets you set alerts for unusual behavior.

A Grafana dashboard might show the number of successful requests and average response times over the last 24 hours. If response times or the number of errors increase, alerts notify your team right away.

With Prometheus and Grafana, you get a clear view of how your APIs are performing, helping you detect issues early and keep users happy.

Securing API endpoints is vital to protecting sensitive data. Here’s how you can ensure your API endpoints are secure:

• Authentication Methods: Authenticate requests using API keys, OAuth tokens, or JWTs (JSON Web Tokens) so that only authorized users can access your endpoints.
• Authorization: Implement Role-Based Access Control (RBAC) to ensure that users only have access to the resources they are authorized to.
• Rate Limiting: Prevent abuse of your API by limiting the number of requests a client can make within a certain time frame.

When designing and working with API endpoints, developers can sometimes make mistakes that hinder the functionality, security, and maintainability of the API. Below are some common mistakes and how to avoid them:

1. Inconsistent Naming Conventions

One of the most common mistakes is not maintaining consistent naming conventions for endpoints. This can lead to confusion and make the API harder to use, especially as it scales. For example, using inconsistent names like /getUser and /fetchUsers for similar actions can confuse developers.

How to Avoid:

Always use a consistent naming convention. Endpoints should represent resources, and actions should be inferred from HTTP methods (GET, POST, PUT, DELETE). For example, use /users for retrieving user information and /users/{id} to get a specific user’s details.

2. Lack of Proper Versioning

API versioning is the practice of including a version number in your API's endpoint, allowing you to update or modify the API without affecting existing clients. For example, you might start with /api/v1/ and later release /api/v2/ as new features or changes are added.

How to Avoid:

Always include versioning in your API URLs, such as /api/v1/ or /api/v2/. This allows you to release new features while keeping the older versions available for existing clients.

3. Ignoring Error Handling

Another mistake is not handling errors properly or providing ambiguous error messages. If a request fails, returning a generic error like 500 Internal Server Error without context can make debugging difficult.

How to Avoid:

Always return clear and meaningful error messages with appropriate HTTP status codes. For example, use 404 Not Found for missing resources and 400 Bad Request for invalid inputs.

{

  "error": "Invalid user ID",

  "message": "The user with ID 9999 does not exist."

}

4. Overloading API with Too Many Features

Including too many features or mixing concerns can make an API bloated and difficult to maintain. For example, combining user management, billing, and product management into a single endpoint can lead to a mess of functionalities within one API.

How to Avoid:

Keep each endpoint focused on a single responsibility. If your API serves multiple purposes, segment them logically into different endpoints, such as /users, /orders, and /products.

5. Not Securing API Endpoints

Failing to secure your API endpoints can expose sensitive data and leave your system vulnerable to attacks. Allowing open access to endpoints without proper authentication and authorization is a significant mistake.

How to Avoid:

Always secure your API endpoints with authentication mechanisms such as API keys, OAuth, or JWT tokens. Additionally, make sure to use HTTPS to encrypt data in transit.

When designing an API endpoints, it’s important to focus on clarity, security, and efficiency. The goal is to create scalable and easy-to-use endpoints that will grow with your application and make life easier for developers working with the API.

Let’s break down the best practices for structuring API endpoints in a way that makes sense for both the developer and the API client.

1. Use Descriptive and Consistent Naming

Start with clear and meaningful names for your endpoints. Consistency is key. Use nouns (e.g., /users, /tests) to represent resources, as HTTP methods define the actions (GET, POST, PUT, DELETE). This keeps the endpoint easy to understand and predictable.

Example: Instead of /runNewTest, use POST /tests when starting a test.

This makes it clear to anyone using the API that the POST method is for creating a new test, and the resource is /tests.

Tip: Keep endpoint names plural when referring to collections of resources (e.g., /users vs /user), as this maintains consistency and follows common naming conventions.

2. Implement API Versioning

APIs evolve over time, and versioning is crucial for preventing breaking changes that could disrupt clients relying on older versions. By adding versioning to your API paths, you ensure backward compatibility while continuing to introduce new features.

Example:

• /api/v1/results for fetching test outcomes (version 1).
• /api/v2/results for a new version that might include filters or additional parameters (e.g., pagination).

Tip: Version your API via the URL path (e.g., /v1/) instead of in headers to keep it explicit and easy to track.

3. Handle Errors Gracefully

Error handling is vital for a smooth user and developer experience. Provide clear, meaningful error codes and messages to help debug issues quickly. This is especially important for testing workflows where resolving problems quickly is essential.

Example:

• 404 Not Found: When the requested resource, such as a test session, doesn’t exist.
• 500 Internal Server Error: When something goes wrong on the server.

Sample error response:

{

  "error": "Resource not found",

  "message": "The user with ID 123 does not exist"

}

Tip: Always ensure that your error responses are consistent in format, helping users easily troubleshoot and understand what went wrong.

4. Use Query Parameters for Filtering and Pagination

To prevent overwhelming the server with large datasets, query parameters are essential for filtering and paginating the data. This is particularly important for endpoints that return large sets of logs, test results, or analytics.

Example: GET /api/v1/tests?status=failed&limit=10&page=2

This request retrieves failed tests in manageable chunks, allowing clients to request smaller datasets, improving performance and usability.

Tip: Implement pagination (e.g., page, limit) to control the amount of data being returned. This will help optimize performance and avoid large response payloads.

5. Ensure Secure Endpoints

Security is a top priority, especially when dealing with sensitive data or authentication tokens. Always use HTTPS for all endpoints and secure authentication methods, such as OAuth or API keys, to protect the data being exchanged.

Example: Use Authorization: Bearer <access_token> in the header for secure access to endpoints.

Tip: Never expose sensitive information, like API keys, directly in the URL. Use headers for authentication to keep data safe.

6. Implement Rate Limiting

Rate limiting is crucial to ensure fair usage and protect your API from excessive requests that could overwhelm the server. By setting a limit on the number of requests a user can make in a specific time window, you prevent abuse and ensure the stability of the service.

Example: Allow only 100 requests per minute per user. If the user exceeds the limit, return a 429 Too Many Requests status code.

Tip: Implement dynamic rate limiting based on user roles or IP addresses to ensure fair distribution of resources.

7. Document Your Endpoints

Proper API documentation is essential for developers to understand how to interact with your API. Clear, detailed documentation helps developers integrate with your API efficiently without guesswork.

Example: Document each endpoint with parameters, expected responses, and error codes. For instance, /api/v1/tests/{id} should document path variables, expected response JSON structure, and errors like 404 Not Found when the test ID is invalid.

Tip: Keep your documentation up to date with the API to avoid confusion and ensure that developers are always working with the latest version of the API endpoint.

In this guide, we have covered the fundamental aspects of API endpoints, including design best practices, common mistakes to avoid, and how to test and monitor them effectively. Follow these best practices to ensure your APIs are scalable, reliable, and easy to maintain, from using consistent naming conventions to implementing versioning and securing endpoints. For APIs to be developer-friendly and secure, these principles must be understood and applied.