7. Are there any recommendations regarding the server upgrades?

The Venice backend is made up of three services: controllers, routers and servers. Typically, we recommend upgrading controllers first, then the rest. The reason for that is that servers have versioned protocols to replicate data between them and if there is a change to that protocol (which is not that common… maybe once per year or so…), then old servers can fetch the schema of the newer protocol from the upgraded controllers. As is usually the case for distributed (replicated, partitioned) systems, we perform upgrades in a rolling fashion, one (or few) nodes at a time.