> Horrified at what must lurk beneath the façade

It's Ruby, which is pretty horrific but still I think there was probably something not quite right in your setup because it isn't normally that slow.

While there are a lot of little knobs that can tweak performance, it shouldn't be slow out of the box, yet it is the number one complaint about GitLab.

yeah we run it on a tiny setup compared to that and it's fine. In fact, impressively snappy if anything.