Looks like they have an interesting range of customers[0] so my take on "why even add the Rust" is because their customers are already using Java, a total rewrite might be considered irresponsible as it would be incompatible with their existing customer base. I do have to wonder though, if some serious Java refactoring in any way, would have helped at all. How many code smells do they have going on in their codebase? Or is it to the best of their knowledge a really clean Java codebase?
Note Discord themselves has used Rust for bottlenecks with Erlang/Elixir/Beam[1].
Note Discord themselves has used Rust for bottlenecks with Erlang/Elixir/Beam[1].
[0]: https://questdb.io/customers/
[1]: https://discord.com/blog/using-rust-to-scale-elixir-for-11-m...