For backends they've standardized on Go and Java, deprecating/eliminating node and python where possible. I understand node is still prevalent for serving react-based frontends, both external and internal facing.
How do they decide with a new backend service to use Go vs Java?
Often comes down to the preference of the engineers in a given team and evaluating pros and cons with engineers outside their team (aka review their plans before they start building)
I'd guess it's usually up to the developers/owning team, but also to some extent depending on the ecosystem it's interacting with (e.g. Hadoop would tend to prefer Java)