[derefr]

I made that very specific comparison for a reason: most "plugin systems" for software (like Apache) act sort of like audio VSTs—they can insert themselves anywhere in the "processing chain" of a request, making following the logic more complex.

Redis modules, like filesystem drivers, are comparatively simple: they register a set of commands that they respond to, and each such command is handled exclusively by that module when received. Less like Apache plugins, more like scripts in a cgi-bin. You don't need to know what else is in the cgi-bin besides your own script, because everything there is entirely independent.