The HTTP method PUT is idempotent and used for updating resources in RESTful APIs. Idempotent means that making the same request multiple times will have the same effect as a single request.

Synthetic monitoring involves simulating user interactions with an API to evaluate its performance. This helps in identifying potential issues, such as slow response times or downtime, before real users are affected. By mimicking user behavior, synthetic monitoring provides valuable insights into the API's functionality and performance under various conditions.

In this scenario, testing for fault tolerance becomes crucial. An API Gateway should gracefully handle failures in backend services to ensure continuous service availability. Fault tolerance testing assesses the system's resilience against potential failures and ensures uninterrupted service.

The 'Mock Server' feature in API testing tools, such as SoapUI or Postman, serves the purpose of simulating the behavior of a real server. It allows testers to conduct testing without relying on actual endpoints, facilitating early testing stages. This simulation helps uncover potential issues and ensures that the API functions as expected. It is particularly useful for testing scenarios where actual endpoints may not be readily available or stable.

Schema validation is essential in data-driven testing to verify that test cases can handle diverse API response formats. It ensures that the data structure conforms to the expected schema, enhancing the robustness of test cases.

Boundary value analysis is a testing technique that explores the behavior of a system at the edges or boundaries of the input domain. In the context of negative testing in APIs, it helps identify potential issues that may arise at the upper and lower limits of input values. By testing extreme values, testers can uncover vulnerabilities that might not be apparent with typical inputs.

API testing is typically performed during each sprint in Agile development. This approach ensures that APIs are tested iteratively, allowing for early identification and resolution of issues, aligning with the Agile principle of delivering working software at the end of each iteration.

SoapUI offers "LoadUI," which allows for extensive functional and load testing of APIs. LoadUI is a performance testing tool integrated with SoapUI to assess the scalability and reliability of APIs under various load conditions.

Monitoring hardware utilization is crucial to identify performance issues and optimize resources during different load conditions, ensuring efficient system performance.

Unit testing is a software testing technique where individual components or functions of a software application are tested in isolation. It occurs before integration testing and ensures that each unit of the software performs as designed.