If you're a small business, you almost never need replicas or pooling. Postgres is insanely capable on modern hardware, and is probably the fastest part of your application if your application is written in a slower dynamic language like Python.
I once worked with a company that scaled up to 30M revenue annually, and never once needed more than a single dedicated server for postgres.
And Postgres upgrades are not transparent. So you'll have a 1 or 2 hours task, every 6 to 18 months that you have only a small amount of control over when it happens. This is ok for a lot of people, and completely unthinkable for some other people.