Servlet filters complement the MVC architecture by providing a mechanism to preprocess requests and post-process responses. They add a layer of functionality that can be applied across multiple components, enhancing the flexibility of the MVC design.

In an MVC framework, a servlet often delegates business logic processing to the controller layer, which is responsible for handling user input and coordinating the application's response.

The servlet forwards the processed data to the view using the forward mechanism, allowing the view to render the updated information based on the servlet's processing.

Servlets in an MVC framework typically receive user input through request parameters, which are data sent by the client as part of the HTTP request and can be accessed by the servlet.

The Front Controller pattern used in MVC frameworks centralizes request handling in a single servlet.

In the MVC framework, servlets are typically used to implement the Controller component, responsible for handling user input, processing requests, and interacting with the model and view components.

In an MVC-based web application, servlets generally fit in the Controller layer. They handle user input, process requests, and coordinate communication between the model and view components.

Caching strategies, for optimizing performance, should be implemented in the Model. The Model is responsible for data access and processing, making it an appropriate place to introduce caching mechanisms.

The primary purpose of encoding user input is to prevent security vulnerabilities, such as Cross-Site Scripting (XSS), by ensuring that user input is treated as data, not executable code.

The Content-Security-Policy (CSP) header can be used to mitigate some types of XSS attacks by defining and controlling the sources from which certain types of content can be loaded.