As someone that has used Hasura very heavily in the past, I can see the operational benefit of not needing to manage one more service.

The talk about memory constraints seems a bit odd though. The extension is still going to require memory and without profiling the alternatives it seems odd to say: "we won't use any more memory with an extension". Especially when you say "these established/stable alternatives fulfill all our feature requirements". In practice I always found Hasura to be reasonably lightweight (I can't speak for PostGraphile).

I think there's an advantage to running this API layer as an additional service in front of the DB though. Then it can act as an API gateway to more than just your database.

Also, the generation of a "Relay style" schema is off putting for me. I'm really not a fan of the style and was one of the biggest advantages for me in using Hasura.