feat: Add Cassandra Wide-Column Backend With Query-First Keys - #9
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ThomasHartDev wants to merge 1 commit into
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feat: Add Cassandra Wide-Column Backend With Query-First Keys#9ThomasHartDev wants to merge 1 commit into
ThomasHartDev wants to merge 1 commit into
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One table per access path, partition keys that colocate a query, and clustering order so a timeline partition is already newest-first.
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Cassandra is the wide-column backend of the activity feed. Each query owns a table: users_by_id, users_by_handle, following_by_user, followers_by_user, posts_by_author, posts_by_id. The partition key colocates the rows for that query, and posts_by_author clusters on (created_at DESC, post_id DESC) so a timeline partition is already newest-first.
There is no join and no cross-partition transaction. Handle uniqueness is INSERT IF NOT EXISTS on users_by_handle; if that LWT loses, the store deletes the users_by_id row. The home feed is one posts_by_author read per followee plus a merge, so unfollow stays live. MemoryCassandra is an in-process engine with the same rules: missing partition key or a non-key restriction throws. Contract tests plus partition, clustering, and LWT cases are green locally.