Definition
One partition receiving far more traffic than the others, becoming a bottleneck while the rest sit idle.
How it works
Caused by a skewed shard key — e.g. sharding by celebrity user, by date (all of today's writes land on one shard), or by a low-cardinality field. Fixes: pick a higher-entropy key, add a hashed/composite key, salt the key, or split the hot range. The symptom is one node at 100% while the cluster looks under-utilised on average.
Common questions
What is Hot Shard?
One partition receiving far more traffic than the others, becoming a bottleneck while the rest sit idle.
How does Hot Shard work?
Caused by a skewed shard key — e.g. sharding by celebrity user, by date (all of today's writes land on one shard), or by a low-cardinality field. Fixes: pick a higher-entropy key, add a hashed/composite key, salt the key, or split the hot range. The symptom is one node at 100%…
What is Hot Shard used for in system design?
Caused by a skewed shard key — e.g. sharding by celebrity user, by date (all of today's writes land on one shard), or by a low-cardinality field. Fixes: pick a higher-entropy key, add a hashed/composite key, salt the key, or split the hot range. The symptom is one node at 100%…