Mostly because the backend services were all in Python and already used Pydantic in a number of places. Prisma was just more heavyweight than what we needed.

We actually started with Postgraphile, but found it was too much magic and eventually moved to defining resolvers explicitly with Strawberry for each service (which was much easier to do once we added the stitching layer).

Interesting. Yeah, I also found Prisma to be a bit heavyweight. Postgraphile is nice, though. I wish it went beyond postgres.