The Simple Common Gateway Interface (SCGI) was created to remove the burden of starting a new process for each request while being simple to implement. Re-using the process is a big win for scripting languages, where the interpreter can stay in memory as the scripts are loaded and cached. The overall goal of SCGI is simplicity of implementation. SCGI was created as a primary interface between python web applications and web servers.

With SCGI, the headers are sent as a concatenation of pairs of zero-terminated strings, so that C programs can use them without copying. The SCGI standard does not specify how the transport between the application and the web server is implemented, as long as it carries a stream of bytes.

SCGI and FastCGI are quite similar, but SCGI gives up backward-compatibility to gain simplicity. Due to the similarities, the Lighttpd SCGI module shares the configuration options of the FastCGI module.