Consistent Hashing Playground: Modulo Hashing Moves 83% of Keys When a Server Joins, Jump Hash 17%

Mon, 05 Oct 2026 00:00:00 +0000

Five cache servers share 100,000 keys. Traffic grows, and you add a sixth. With the obvious rule, hash the key and divide by the number of servers, 83% of the keys now belong somewhere else. Most of them move between servers that never changed. For a cache that’s a wave of misses landing on the database at once. For a store it’s a mountain of data copied across the network for no reason.

What Is a Key-Value Store? Redis, Valkey, DynamoDB and etcd Explained

Mon, 05 Oct 2026 00:00:00 +0000

A key-value store files every value under a key. You hand it a key and a value to keep, and later you hand it the key and get the value back. That’s the whole contract. Think of a coat check: you get a ticket, and the ticket is all anyone needs to find your coat. Nobody goes through the coats looking for a blue one.

That simple contract is why key-value stores are fast. Finding a value by its key is a direct jump, through a hash table or a sorted tree, with no query to plan and no tables to join. It’s also why they spread so well over many machines: if every request names its key, the key alone says which machine to ask.

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Consistent Hashing Playground: Modulo Hashing Moves 83% of Keys When a Server Joins, Jump Hash 17%

What Is a Key-Value Store? Redis, Valkey, DynamoDB and etcd Explained