This type of engineering comes into account when the person know about the end results before hand and he has to find out the logic behind those results. In dynamic malware analysis, the specialist first run the malware in an isolated environment and then from its behavior predicts the techniques used in building the malware.
In Forward Proxy, we realize that how an end user can use this service to become anonymous. In reverse proxy, the end system which the user is trying to access will be using proxy to intercept and filter requests from the users. The main use of a reverse proxy is that it helps to reduce unwanted traffic on the server and prevents DDOS. It adds an additional layer of security.