A seed past a float overflowed the shuffle's start point, and a cursor holding Infinity or a 400-digit
key overflowed its int/float read: both answered 500. The routes bound the seed (422), the start
point folds it to 32 bits, and the cursor read counts an overflow as a bad cursor (400). A plan test
holds that the walk reads ix_videos_shuffle_key with no sort over a realistic scope.
Every video carries a random number drawn once (videos.shuffle_key, migration 0118, indexed with
id). A seed picks a point on that ring: the feed's Shuffle sort pages along it and wraps, and the
Home surprise reads a 500-video window of it and shuffles that window by the seed, so no video is
favoured for sitting after a wide gap. The md5(id || seed) order read and sorted the whole feed
scope on every call: ~350 ms on prod per surprise, 381-767 ms per Shuffle page on localdev, now
14 ms and 4 ms.
peter