"Lightroom (hardly bloatware, it's actually pretty efficient) uses SQLite for its database"
It's probably a bit of exaggeration to describe it as "efficient". It needed a beast of a machine spec to run at all when it was in beta stage, though it's probably been streamlined a bit since - I now have a decent machine to run it on anyway, as I had to upgrade to run it. I find the Lightroom DB searches very sluggish, though this is probably not SQLites fault.
As a comparison, I previously used RawShooter from Pixmantec which Adobe swallowed and killed (hence my need to move to Lightroom). At the core, this did pretty much the same thing as Lightroom (metadata based image alterations applied on the fly), but did it faster and this on my ageing W2k desktop with 384Mb RAM (ok, ok, so I did need to upgrade anyway!)
I'm not knocking Lightroom, I use it a lot, and am very happy with what it does for the most part, but I do think it's resource heavy in the same way as pretty much the rest of the Adobe stable.