What is Consistent Hashing? How is it used in Distributed Systems?

Difficulty: 6/10

hash ring, node churn, load balancing

Consistent Hashing

Consistent Hashing is a partitioning technique that maps both keys and nodes onto a logical hash ring. A key is assigned to the next node on the ring according to the chosen traversal rule. Its main advantage is that when nodes are added or removed, only a relatively small portion of keys need to move compared with naive hashing based directly on modulo node count.

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1
Reduces data movement when cluster membership changes.
2
Commonly used in distributed caches and partitioned storage systems.
3
Virtual nodes improve distribution and reduce hot spots.
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Replication can assign a key to multiple successive nodes.
5
The hash function and node placement influence load distribution.
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Consistent hashing does not automatically provide replication, consistency, or fault tolerance; those are separate system-design concerns.

Scenario Questions

0-2 years experience

2-5 years experience

1Our service uses consistent hashing for sharding data, but after a node failure we see a spike in latency for certain keys. What could be causing that and how would you investigate?

Follow-up Questions