Redis Cluster and Hash Slots

What you'll walk away with

Explain the core ideas behind Redis Cluster and Hash Slots
Run the sample Redis command or code and verify its output
Apply the technique correctly to the Tutorial Platform and production scenarios

Build the mental model

Redis Cluster divides the keyspace into 16,384 hash slots distributed among primary nodes. Clients must understand MOVED and ASK redirects. Hash tags inside `{...}` place related keys in one slot for multi-key commands or scripts, but broad tags can create a hot shard. Cluster adds horizontal capacity and operational complexity.

Connect it to a real scenario

Name coupon-script keys `coupon:{42}:remaining` and `coupon:{42}:claims` so they share a slot. Verify with CLUSTER KEYSLOT, monitor node and slot health, and test rolling maintenance and resharding. If one node still fits the workload, Sentinel may remain simpler.

Cluster uses 16,384 slots
Multi-key operations need one slot
Hash tags provide locality but can cause hotspots

Try the working example

shell

CLUSTER INFO
CLUSTER NODES
CLUSTER SLOTS
CLUSTER KEYSLOT coupon:{42}:remaining
CLUSTER KEYSLOT coupon:{42}:claims
CLUSTER COUNTKEYSINSLOT 9030

You should see

You can inspect cluster health, node ownership, and confirm related keys share a slot.

5-minute try-it

Design a tenant hash-tag strategy and explain noisy-tenant hotspot mitigation.

One important caution

Do not tag every key of a large tenant with one `{tenant}` value; it can eliminate sharding benefits.

Redis — Cluster Specification — Redis

Easy traps

Do not tag every key of a large tenant with one `{tenant}` value; it can eliminate sharding benefits.
Validate sample commands on a local or test instance with recoverable data before applying them to production Redis.

Exercise

Design a tenant hash-tag strategy and explain noisy-tenant hotspot mitigation.

You'll know it worked when: You can inspect cluster health, node ownership, and confirm related keys share a slot.