Backend & systems·Caching and invalidation
one key gets so much traffic that the single node holding it is saturated while the rest of the cluster sits idle.
Hot key
Also calledhot spot, hot partition
A single key or partition receiving a disproportionate share of requests, so that sharding does not help: the load lands on one node regardless of how many you add. Typical causes are a celebrity record, a global counter, or a partition key with low cardinality. The mitigations are key splitting, a local cache in front of the shared one, or request coalescing.