Why does Cassandra not support JOINs and how do you handle relationships?

Cassandra is distributed — a JOIN would require querying across potentially different nodes for each row, which is O(n²) in the worst case for a large table. This would destroy performance. Solution: query-first schema design and denormalization. For a blog platform: Don't have posts table + authors table + JOINed query. Instead: Create posts_by_author table with all needed author fields duplicate