Hmm, I thought I had everything setup properly, but apparently I was wrong. I am getting constant restarts in the prefect container with the following error:

ConnectionRefusedError: [Errno 111] Connect call failed ('10.43.121.165', 5432)

The error is happening when trying to run migrations on startup. That is the correct internal cluster IP that it resolved to (I used the hostname in the connectionstring). I also did some tests to make sure that the container should be able to connect:

kubectl exec -it -n test-client prefect-server-6888d4cbf8-6fcm8 -- /bin/bash

and then:

python3 -c '
import asyncio
from sqlalchemy.ext.asyncio import create_async_engine

async def test_sqlalchemy():
    try:
        engine = create_async_engine("<postgresql+asyncpg://app:mypassword@goacquire-cluster-prefect-rw:5432/app>")
        async with engine.connect() as conn:
            print("SQLAlchemy connection successful!")
    except Exception as e:
        print(f"SQLAlchemy Error: {e}")

asyncio.run(test_sqlalchemy())
'

which returned

Successfully connected!