So, for the sbt project we noticed significant resolution time improvements with the following patch:
A lot of artifacts being resolved use Maven's "dependencyManagement" conventions
Ivy appears to turn these into "exact matcher" rules
A ton of resolution time is spent filtering through these rules
The existing solution is O for all overrides
What the patch does:
Creates a key'd store for all "exact matcher" rules
When executing rules, ensure that we only traverse what we have to (non-exact, exact specific to our key and "default").
As I said, this represents a significant speed bump for sbt builds using Ivy. All existing tests pass, and I think they cover this aspect of ivy pretty well, from what I could see.