There are a few rust solutions in the "Show and Tell" linked above, for example this fairly readable one at 15.5s: https://github.com/gunnarmorling/1brc/discussions/57 A comment above referencing Python "polars" actually has rust polars, std, and SIMD solutions as well (SIMD was fasted, but less readable for a hobbyist like me).

EDIT: https://github.com/Butch78/1BillionRowChallenge/tree/main