Something you may find interesting is that the new faster maps are loosely based on Rich Hickey's HAMT implementation that is used in Clojure. Jose and co. in Elixir adapted/is-adapting their internals to use maps as well, as they were faster than any implementation they had.<p>In addition, I wrote a full QuickCheck model for the new maps. That is, we randomly generate unit test cases for the maps and verify them. We have generated several millions of those test cases, including variants which heavily collides on the hash. This weeded out at least 10 grave bugs from the implementation, which in turn means this release is probably very stable with respect to maps.