I don’t think sharding is a big issue for application development. It adds overhead to devops/sre teams though, especially in the case of resharding. I have see

I don’t think sharding is a big issue for application development. It adds overhead to devops/sre teams though, especially in the case of resharding. I have seen worst issues and overhead to dev team caused by bad table partitioning schemes, not sharding. Imo the biggest challenge of rdbms in modern saas is hybrid (oltp + olap) query pattern. Any cloud managed service that is going to nail this in a costly efficient manner will become the next mainstream thing.