ISAPI - Microsoft's Internet Server APIISAPI is a high performance replacement for CGI.
It's advantages include: in-process operation, remaining in memory, direct data transfers and direct socket access.
Unlike some other CGI alternatives, ISAPI is simple and easy to support.
It's down side is that it is not COM or SOM compliant, but then neither was CGI. The major up side is that it is light-weight and fast.