Not sure how it is today, but in the 90s and early 00s when I worked at Ericsson Mnesia had a number of systems that it was used in. There was interestingly 4 DBMSs developed at Ericsson in the 90s and 00s. Mnesia and NDB Cluster as mentioned and two internal DBMSs, TelORB and DBS, I had interesting discussions with all of them and worked with DBS before developing NDB Cluster. We were all situated within 5 minutes walking distance :)
The reliability of OVH has so far not been a problem. Performance is mostly a factor of the VM instances that you use, AWS has much more instances to choose from, but obviously at a much higher cost, so performance per dollar is obviously better with OVH.
There are lots of alternatives for database solutions with Kubernetes, in Hopsworks we use RonDB which is highly available and has a MySQL interface but also supports a REST API and even a prototype Redis service.
One obvious benefit of OVH compared to Hetzner is the S3 storage, the Kubernetes framework and a number of other services provided by OVH, don't think Hetzner would provide those services.
Hopsworks has a platform with a high-availability database (RonDB), a highly available distributed file system (HopsFS) and the services are also redundant. Hopsworks even supports failover to another region. So the software is very reliable. But given that, OVH is a proper cloud vendor and not only a budget hoster, so it has fault tolerant services as well. We use other European companies for budget hosting of our development systems.
New VM types using Intel/AMD VMs of the 4th generation in GCP is compared to 2nd generation VMs. Benchmark is Sysbench and database is RonDB (www.rondb.com).
