I would be extremely (but prepared to be) surprised if Phoenix + Hasura were faster in terms of latency than Phoenix + Absinthe, since one has to enter and exit

I would be extremely (but prepared to be) surprised if Phoenix + Hasura were faster in terms of latency than Phoenix + Absinthe, since one has to enter and exit two vms and the other doesn't, unless you're suggesting the frontend issue graphql results directly to the hasura backend, bypassing phoenix.