Cassandra CQL - clustering order with multiple clustering columns

Your query example restricts user_id so that should work with the second table format. But if you are actually trying to run queries like

SELECT * FROM myCF
WHERE website_id = 30 AND item_id = 10
AND date > 'some_date'

Then you need an additional table which is created to handle those queries, it would only order on Date and not on user id

Create Table LookupByDate ... PRIMARY KEY ((website_id, item_id), date)