Man, reading that made me wish Clustrix (YC '06) open sourced their database (https://www.clustrix.com/). They had a MySQL compatible scale our DB nearly 10 years ago, wireline compatible with MySQL without using any MySQL code, could participate in a MySQL replication cluster with normal MySQL servers (made migration easy). It was scale out shared-nothing, writes would scale linearly as you added nodes, unlike POLARDB which is shared-everything with a single master. It used RDMA 10 years ago, and custom PCIe devices because NVMe didn't exist.

But they didn't open source it, so only a small handful of companies get to use it. Sad.