In a pre-AST project 2 world, I've found the following 4 languages work well for programming (non-frontend) use cases, based on my startup experience:

- Java (with JOOQ): As a high level typed language (similar to Hack for Meta's use case. If Golang's generics help create a JOOQ equivalent in the future, then this would be Golang).

- C++/Carbon: As a systems/performance language. (We haven't tried Carbon yet, but this I feel would help beat Rust for this systems category)

- JS/TypeScript (Node or Deno or zx): As a scripting/tools language.

- Python: As a data processing and machine learning language (primarily thanks to the JIT computing and data libraries for Python). (This list ignores CUDA :))

Update update: Or reluctantly with Python instead, with a similar library such as PugSQL.