Comment by cavisne
AWS has a cool general approach to this problem (one badly behaving user effecting others on their shard)
https://aws.amazon.com/builders-library/workload-isolation-u...
The basic idea is to assign each user to multiple shards, decreasing the changes of another user sharing all their shards with the badly behaving user.
Fixing this issue as described in the article makes sense, but if they did shuffle sharding in the first place it would cover any new issues without effecting many other users.
I think shuffle sharding is beneficial for read-only replica cases, not for writing scenarios like this. You'll have to write to the primary and not to a "virtual node". Right? Or am I understand it incorrectly? I just read that article now.