@dnolen & @alexmiller I've gotten hash perf speedups for Lean HAMT's of around 2 - 4x for all JS engines. I also realized that I wasn't testing maps with hash collision 😞. So I've been working on removing those bugs. I'll be running perf tests on maps with hash collisions once I get all of these bugs fixed. One more thing I found out why Firefox perf for sequences is 2x slower then all other JS engines. It doesn't like doing array allocation at all so the arrays used to hold the stack for sequences are the root of the slowdown .