How does this avoid nodes doing stale reads from the inmemory copy resulting in each node having a slightly different out-of-date view of the cluster?
However, those cases are fine. If a database was created and a server doesn't have a copy of it. When a write comes in it'll be a cache miss so it'll hit the Raft system to get the info.
In the case of a new server joining the cluster, it won't get new data assigned until a shard group gets created and a shard gets assigned to it. When a write comes in if a node doesn't have a shard group for that time range, it'll all out to the Raft system to get the information.
So yes, it's possible for some servers to have a stale view of this cluster metadata, but we work around it by having them request the information on demand and periodically refresh the entire thing.