Around 11:14 UTC today one switch of the private network went down and required a reboot. The problem has been solved but this resulted in a downtime of about 8 minutes.
Note that this is the issue with the new database server, if the link between the application server and the database server goes down, then the service is down. I will contact the support staff of OVH as in my understanding, they had a kind of redundant system to not rely on a single router.