The short answer is that we tried, back in 2020, while working on a central bank payment switch by the Gates Foundation. We found we were hitting the limits of Amdahl's Law, given Postgres' concurrency control with row locks held across the network as well as internal I/O, leading to the design of TigerBeetle. To specialize not for general purpose but only for transaction processing.
On the one hand, yes, you could use a general purpose string database to count/move integers, up to a certain scale. But a specialized integer database like TigerBeetle can take you further. It's the same reason, that yes, you could use Postgres as object storage or as queue, or you could use S3 and Kafka and get separation of concerns in your architecture.
I did a talk diving into all this recently, looking at the power law, OLTP contention, and how this interacts with Amdahl's Law and Postgres and TigerBeetle: https://www.youtube.com/watch?v=yKgfk8lTQuE
On the one hand, yes, you could use a general purpose string database to count/move integers, up to a certain scale. But a specialized integer database like TigerBeetle can take you further. It's the same reason, that yes, you could use Postgres as object storage or as queue, or you could use S3 and Kafka and get separation of concerns in your architecture.
I did a talk diving into all this recently, looking at the power law, OLTP contention, and how this interacts with Amdahl's Law and Postgres and TigerBeetle: https://www.youtube.com/watch?v=yKgfk8lTQuE