Resharding hash slots in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is resharding in Redis Cluster?

Resharding is the process of moving hash slots from one Redis node to another to balance data and load across the cluster.

beginner

How many hash slots does a Redis Cluster have?

A Redis Cluster has 16,384 hash slots numbered from 0 to 16,383.

beginner

Why do we need to reshard hash slots in Redis?

We reshard hash slots to evenly distribute data and requests among nodes, improving performance and avoiding overload on any single node.

intermediate

What command is used to move a hash slot from one node to another in Redis?

The command used is CLUSTER SETSLOT <slot> MIGRATING <node-id> along with CLUSTER GETKEYSINSLOT and MIGRATE to move keys.

intermediate

What happens to client requests during resharding of hash slots?

Clients may receive a MOVED response telling them to redirect requests to the new node owning the slot, ensuring smooth operation during resharding.

How many hash slots are there in a Redis Cluster?

A 512

B 1024

C 16384

D 65536

Redis Cluster divides data into 16,384 hash slots for distribution.

What is the main goal of resharding hash slots in Redis?

A To encrypt data

B To backup data

C To delete unused keys

D To balance data and load across nodes

Resharding moves hash slots to balance data and workload among cluster nodes.

Which Redis command helps identify keys in a specific hash slot?

A CLUSTER GETKEYSINSLOT

B GETKEYS

C KEYS

D CLUSTER KEYSLOT

CLUSTER GETKEYSINSLOT lists keys in a given hash slot.

During resharding, what response might a client receive if it queries a moved slot?

A MOVED

B ERROR

C ASK

D OK

Clients get a MOVED response to redirect to the new node.

What is the first step in resharding a hash slot in Redis?

A Delete keys in the slot

B Set the slot to importing state on the target node

C Migrate keys to the target node

D Restart the cluster

The target node must mark the slot as importing before receiving keys.

Explain the process and purpose of resharding hash slots in a Redis Cluster.

Think about how Redis keeps data balanced and how clients know where to find keys.

Describe what happens to client requests when a hash slot is moved to a different Redis node.

Consider how Redis tells clients about the new location of data.