Are there any system or operational considerations to creating a large number of tables within a key space? e.g. creating one table per user in a scenario where they may be thousands of users?
Having big number of tables would have an effect on topology changes, it would slow them down.
It would slow down any other operation that works per table, like repairs backups.
We are testing with 5000 tables in one keyspace regularly
Same reasons as in cassandra:
Impacts of many tables in a Cassandra data model.
It’s not recommended, scylla is known to work with a few thousand tables, but it has a price. and I would recommend measuring it before hand, that you are willing to pay it
What about num of keyspaces? If we use Alternator interface, it will create a separate keyspace for each table, so the number of keyspaces is equal to the number of tables.
Many keyspaces cause problems of similar nature to may tables. They bloat data structures and everything involving keyspaces will take longer.
Just to clarify, by many, I mean thousands. I think you should be fine with a 3 digit number amount of them.