API gateway request transformation policies offer significant flexibility and power for developers needing to modify the structure and content of incoming requests to better fit their APIs. These transformations can be particularly useful when transitioning between API specifications, correcting longstanding documentation errors, or enhancing security by filtering sensitive data. The text explores the use of request transformations via the Kong Gateway and its built-in Request Transformer plugin, which allows developers to manipulate headers, query strings, request bodies, and HTTP methods. Through practical examples, the text demonstrates various transformations such as copying API keys from query strings to headers, sanitizing sensitive data, and converting request methods, all of which can be configured effortlessly within Kong's declarative setup. The ability to perform these transformations at the gateway level without altering the upstream service provides developers with a versatile tool to maintain seamless API operations while addressing evolving requirements.