> I'd agree in general, but Redis is architected in a way where these features aren't really new "layers", but rather just horizontal modular additions.

> A new data structure + associated commands being supported in Redis is like, say... a new filesystem being supported in the Linux kernel. It's a few files that you could just avoid compiling in if you didn't want them, and which add code-paths that are never run unless you intentionally use that specific new thing.

Isn't it exactly how features are implemented in Apache? Most people think that Apache is too bloated, but the same people also leave a lot of those modules enabled without trying to spend time to understand if they actually need them.

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.