so as far as i can tell it's not like a full switch per se but reddit has services written in both python and go.

r2 (old reddit, the reddit API, some parts of new reddit, some of their ML stuff), their monolith, is still written in python.

some services they have in go include some real time services (like the reddit talk stuff seems to be primarily written in go)

reddit kinda seems to have a SOA (not microservices). while there are some codepaths that go through r2 (and indeed this seems to be the case in a lot of cases with regards to old reddit), a lot of newer code uses services.

(note: their engineering blog (/r/RedditEng) calls a lot of their stuff microservices and indeed they may be using that for some things but a lot of their stuff have been described as using more of a SOA vs a microservices.)

someone like /u/ketralnis may have more information as well?