It's a bit of a shame that Rust's stdlib doesn't have a "fast but less safe" hasher. It's one of the easiest performance optimizations in my experience because it's very rare that an attacker controls input to your hashmap in a way that can actually lead to a DOS.

Not that it doesn't happen, it's just not something I've run into.

Just today I was testing out the performance difference hashing some Scylla queries and got nearly 2x faster hashing moving to fxhash.