API Interview Questions and Answers
Q: What is the difference between SOAP and REST APIs?
A: SOAP (Simple Object Access Protocol) is a protocol for exchanging structured data over the web using XML. REST (Representational State Transfer) is a architectural style for designing web services that uses HTTP and supports a variety of data formats, including JSON and XML. A real-time example is that SOAP is often used for enterprise-level applications that require complex messaging and reliable delivery, while REST is commonly used for mobile and web applications that require quick and flexible data access.
Q: How do you test API integrations with third-party systems?
A: To test API integrations with third-party systems, you can use tools such as Postman or cURL to send requests to the API endpoints and verify the response data. You can also use mock servers to simulate third-party API responses and test your API's integration with them. A real-time example is that if you are integrating with a payment gateway API, you can test the integration by sending requests to the API endpoints for processing payments and verifying the response data.
Q: What is API versioning, and how do you handle it?
A: API versioning is the process of managing changes to the API over time, while maintaining backward compatibility with existing clients. You can handle API versioning by using version numbers in the API endpoints, adding new endpoints for new functionality, and deprecating old endpoints over time. A real-time example is that if you are updating your API to support a new data format or functionality, you can release a new version of the API with a new version number, and provide documentation for developers on how to migrate to the new version.
Q: How do you handle authentication and authorization in API testing?
A: To handle authentication and authorization in API testing, you can use methods such as OAuth 2.0, API keys, or token-based authentication. You can also test different scenarios such as valid and invalid credentials, revoked or expired tokens, and permission levels for specific API functions. A real-time example is that if you are testing an e-commerce API, you can test the authentication and authorization by sending requests with valid and invalid credentials, and verifying the response data for different user roles, such as customers and administrators.
Q: How do you ensure API reliability and stability?
A: To ensure API reliability and stability, you can use techniques such as performance testing, load testing, and monitoring for errors and response times. You can also implement caching and throttling to reduce server load and improve response times. A real-time example is that if you are testing a weather API, you can test the reliability and stability by sending requests with different parameters and verifying the response data for accuracy and consistency.
Q: What is API documentation, and why is it important?
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A: API documentation is a set of guidelines, instructions, and examples that describe the API functions, data formats, and usage. It is important because it helps developers understand and use the API correctly and efficiently, reduces the learning curve, and improves the API adoption and usability. A real-time example is that the Twilio API documentation provides detailed information on how to send and receive SMS messages using the Twilio API, including API endpoints, data structures, and code examples.
Q: What is endpoint testing, and how do you perform it?
A: Endpoint testing is a type of API testing that focuses on testing the API endpoints, which are the URLs that can be used to access the API functions. To perform endpoint testing, you can use tools such as Postman or curl to send HTTP requests to the endpoint and verify the response status code, headers, and data. A real-time example is that if you are testing a social media API, you can test the endpoint for retrieving user
Q: How do you ensure API security, and what are some examples of security vulnerabilities?
A: To ensure API security, we can follow certain measures like implementing SSL encryption, using authentication and authorization mechanisms like API keys, OAuth, JWT tokens, and implementing proper access controls to restrict access to sensitive resources. We can also use tools like firewalls, intrusion detection systems, and vulnerability scanners to identify and mitigate potential threats. Some common examples of security vulnerabilities in API include:
Q: How do you handle API errors, and what are some examples of error handling techniques?
A: To handle API errors, we can implement proper error handling techniques like returning meaningful error codes and messages, handling exceptions, logging errors, and providing detailed error responses to users. We can also use tools like error monitoring services and logging frameworks to track and analyze errors. Some common examples of error handling techniques include:
Q: What is Data Injection in API Testing?
A: Data Injection is a type of security vulnerability in which an attacker injects malicious data into the API call to manipulate or compromise the system. This can happen if the API is not properly validated or sanitized to prevent unauthorized data from being processed. An example of data injection could be an attacker manipulating an API call to change the SQL query being executed, which could allow them to retrieve sensitive data from the database. In API testing, we can identify and prevent data injection by thoroughly testing input validation and sanitization mechanisms and implementing proper access controls and security measures.