It's relatively easy to adjust this setup to use synchronous replication. In fact, it's something that I expect we'll be offering to customers in the future. Most people we talk to aren't willing to sacrifice the write availability or performance synchronous replication requires. We mostly try to give them the tools to do it right, and then educate them on the tradeoffs.

(disclaimer, I work for Compose)

Is it even possible to guarantee that you won't lose commits with postgresql replication? For many applications, consistency is more important than not losing any data ever. For the other kind of application, you'll need something else.