We replaced a little over 80k lines of Erlang with around 50k lines of Rust (not all at once of course). The biggest change was memory usage went way down. Erlang likes to run on nodes wth huge amounts of RAM for process mailboxes. We cut down our peak usage by almost 30%. That’s huge. Latency is also significantly better for the percentiles we’re looking at. The best part is that the code base is way easier to manage, and it’s much easier to keep adding to the code add without causing regressions.