It's probably a misconception that database-level transactions are the primary way to implement business transactions - many business processes w/ customers or 3rd parties rely on ACKs and/or compensating transactions, escaping the scope of a single database-level transaction.

In practice, if the services are loosely-coupled enough, transactional boundaries will be local in scope and transactions spanning multiple services are unnecessary. Downstream services can be eventually consistent if idempotency is guaranteed and retries/replays are free.

Inside the scope of a single service, when needed, we use Datomic, which provides ACID guarantees for that (https://docs.datomic.com/on-prem/acid.html) and also helps w/ idempotency guarantees by allowing time-travel (https://docs.datomic.com/on-prem/getting-started/see-histori...).