ReferenceGlossary
Hot key
One key that receives a very large share of reads or writes, such as a celebrity's profile. The one shard or server that owns it saturates while the others stay idle, so adding servers does not help.
Data
In Quorum#
In the Hot key Incident (Series C), 30% of the reads on a busy Cache or Wide-column Store ask for one key on one shard. That Node's capacity divides by 0.3 × its shards + 0.7, so a size-4 Node keeps about half. Hybrid fan-out lets you turn on key splitting for that Node, which spreads the hot key and ends the loss.