Common strategies for API versioning include URL versioning (e.g., "/v1/endpoint"), header versioning (e.g., specifying the version in HTTP headers), and content negotiation (accepting different response formats based on version). These methods allow for evolving APIs while maintaining compatibility.

The goal of API monitoring and analytics is to continuously track an API's health and usage, detect issues, and analyze data for insights. It helps ensure reliability, security, and performance while optimizing resource allocation.

ASP.NET Core ensures the scalability and performance of APIs through support for asynchronous programming. This allows APIs to handle a large number of concurrent requests efficiently by not blocking threads, making it suitable for high-demand scenarios.

The "Content-Type" header in an HTTP request can be used to specify the format of the data being requested from a Web API. It indicates the media type (e.g., JSON, XML) of the data being sent or received, allowing the server to process the request appropriately.

During API development, testing tools can help identify issues such as endpoint errors or data inconsistencies. These tools are crucial for detecting and addressing problems in the API's functionality, ensuring that it behaves as expected and delivers the correct data. Effective testing tools can include unit testing frameworks, integration testing, and automated testing suites.

A Public API is accessible to anyone and does not require special permissions for use, while a Private API has restricted access and is typically used within an organization or by specific authorized users. Public APIs may have usage limitations or require authentication, while Private APIs are usually for internal or controlled use.

Developers may choose to create a Web API instead of a traditional web application to enable integration with other systems. Web APIs allow different software applications to communicate and interact, making them ideal for data exchange and third-party integrations. Providing a graphical user interface, offering a mobile app, or improving website performance may be goals but are not primary reasons for creating a Web API.

When implementing API key rotation, it's crucial to consider security best practices. API keys should be changed periodically to reduce the risk of unauthorized access. Sharing keys with everyone or storing them in public places should be avoided. Storing keys securely, managing access, and ensuring that compromised keys can be revoked are important aspects of API key rotation.

GraphQL allows for more flexibility in querying data compared to REST because it enables clients to specify the structure and fields of the response, allowing them to request only the data they require. In contrast, REST often returns fixed data structures, and clients must make multiple requests to retrieve the needed data.

Load testing an API involves assessing its performance under a specific load. This test measures how well the API can handle a high volume of concurrent requests or transactions, helping identify performance bottlenecks and ensuring the API's reliability under heavy usage.