Systems Design Concepts Practice Test

Hot key problem happens when one cached item becomes extremely popular and all requests hit the same cache node, creating a bottleneck and higher latency. A practical mitigation is to replicate that hot key across multiple cache nodes, so the read load is distributed among several machines. This reduces pressure on any single node, boosting throughput and lowering tail latency, though you’ll need to keep replicas synchronized (write propagation or eventual consistency). Disabling the hotspot isn’t practical and defeats caching benefits, storing the hot key in a separate database slows access, and evicting it constantly just creates misses and churn.