It seems to me that the benefit of Workers is that they run geographically near the user. If the Worker is calling a database that may or not be close to your user, what is the point? You are going to pay the latency cost either from the user to the Worker or the Worker to the DB.<p>I realize that there are some advantages. The network between the Worker and a Google datacenter is probably much faster than the network from the user to the Worker. Also, Firestore in particular can be geographically replicated so that the database is closer to your user. But I'm not convinced that these benefits outweigh a more traditional (and more flexible) architecture.
I can't wait to try out Workers. I've always found "serverless" interesting in concept but the cold starts and vague pricing keep me away. It's pretty cool that Workers actually makes latency better rather than neutral/worse.