That's a very good point. I suspect it will depend a lot on what the largest PG users contribute back, in order to make it scale. For MySQL, the largest users

That's a very good point. I suspect it will depend a lot on what the largest PG users contribute back, in order to make it scale. For MySQL, the largest users were (and still are) the biggest drivers of scalability-related features... and that's despite MySQL being far less of a community-driven open source effort than PG. From my perspective, the biggest roadblocks for PG adoption at high-volume OLTP use-cases are its historical weakness in replication options, its process-per-conn model, and its lack of clustered index support. PG replication is improving at a great rate, especially with the addition of logical replication, but the overall spread of options is still behind MySQL (re: multiple kinds of logical replication; multiple options for async vs semi-sync vs sync replication; large ecosystem of tools to interact with the replication stream). The other two issues are a bit more fundamental. But given the number of excellent engineers working on PG, I'm sure that solutions will be developed in the near future.