Client-side cluster support in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is client-side cluster support in Redis?

Client-side cluster support means the Redis client handles the distribution of data across multiple Redis nodes automatically, so the client knows which node to contact for each key.

intermediate

How does a Redis client know which node to contact in a cluster?

The client uses a hash slot algorithm to map each key to a specific slot, and each slot is assigned to a node. The client keeps track of this mapping to send commands to the right node.

beginner

Why is client-side cluster support important for Redis scalability?

It allows Redis to scale horizontally by spreading data across many nodes, and the client can efficiently route requests without needing a central proxy.

intermediate

What happens if a Redis cluster node moves slots to another node?

The client receives a MOVED response and updates its slot-to-node mapping to send future requests to the new node.

advanced

Name one challenge of client-side cluster support in Redis.

One challenge is keeping the client's slot mapping up to date when the cluster topology changes, which requires handling redirection responses and refreshing the mapping.

What does the Redis client use to decide which node stores a key in a cluster?

A Round-robin

B Random selection

C Hash slot algorithm

D Central proxy

The Redis client uses a hash slot algorithm to map keys to specific nodes.

If a Redis client gets a MOVED response, what should it do?

A Update its slot mapping and retry the command

B Ignore and retry the same node

C Restart the client

D Send the command to all nodes

A MOVED response means the slot has moved; the client updates its mapping and retries.

Why is client-side cluster support better than using a proxy?

A Slows down requests

B Increases complexity

C Requires more servers

D Reduces latency by direct node communication

Client-side support reduces latency by avoiding a proxy and contacting nodes directly.

What is a hash slot in Redis cluster?

A A password for authentication

B A range of keys assigned to a node

C A backup node

D A command type

A hash slot is a range of keys mapped to a specific node in the cluster.

How many hash slots does Redis cluster have by default?

A 16384

B 1024

C 65536

D 512

Redis cluster uses 16384 hash slots by default.

Explain how client-side cluster support works in Redis and why it is useful.

Think about how the client knows where data lives in a cluster.

Describe what a Redis client should do when it receives a MOVED response from a cluster node.

This response tells the client the data moved.