Can you explain what is meant by a middleware sequence in the request processing process?

The middleware sequence is a chain of intermediate handlers through which an HTTP request passes before reaching the application's final logic and back when forming a response. Each middleware receives the request, can perform some logic (for example, authentication, logging, data modification), then pass control to the next middleware or terminate the processing.

For example, in Python web frameworks (Flask, Django, FastAPI), middleware allows dividing processing into stages, improving readability and reusability of code. The sequence is important because the order of middleware affects the processing result.

An example of a simplified middleware chain:

def middleware1(request, next):
    print("Middleware 1: before next")
    response = next(request)
    print("Middleware 1: after next")
    return response

def middleware2(request, next):
    print("Middleware 2: before next")
    response = next(request)
    print("Middleware 2: after next")
    return response

# During request processing, it will pass through middleware1, then middleware2, then to the final function