Resharding hash slots in Redis - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of the resharding command status?

After initiating a resharding operation in Redis Cluster, you run the command CLUSTER RESHARDING STATUS. What output do you expect if the resharding is currently moving slots?

A An error message stating the command is unknown

B An empty list indicating no resharding in progress

C A list showing the number of slots moved and the total slots to move

D A string with the cluster node IDs only

💡 Hint

Think about what information you want to see during resharding progress.

The CLUSTER RESHARDING STATUS command does not exist in Redis. Resharding progress is typically monitored via redis-cli or external tools.

🧠 Conceptual

intermediate

Why is resharding hash slots necessary in Redis Cluster?

Which of the following best explains why you would perform resharding of hash slots in a Redis Cluster?

A To encrypt data stored in hash slots

B To clear all data from the cluster quickly

C To upgrade Redis version on all nodes simultaneously

D To rebalance data when adding or removing nodes to maintain even load

💡 Hint

Think about cluster scaling and data distribution.

Resharding moves hash slots between nodes to balance data and load, especially when nodes are added or removed.

📝 Syntax

advanced

Which command syntax correctly moves 50 hash slots from one node to another?

You want to move 50 hash slots from node A to node B in a Redis Cluster. Which command syntax is correct?

A redis-cli --cluster reshard <cluster_ip>:<port> --slots 50 --from <nodeA_id> --to <nodeB_id>

B CLUSTER RESHARD --slots 50 --from <nodeA_id> --to <nodeB_id>

C CLUSTER SETSLOT 50 NODE <nodeB_id>

D CLUSTER MOVE 50 FROM <nodeA_id> TO <nodeB_id>

💡 Hint

Consider the official redis-cli cluster management commands.

The redis-cli --cluster reshard command with appropriate flags is the correct way to reshard slots between nodes.

🔧 Debug

advanced

Why does the resharding command fail with 'MOVED' error?

You run the resharding command to move slots but get an error: MOVED 1234 10.0.0.2:7002. What is the most likely cause?

A The Redis version is incompatible with resharding

B The slots you want to move are already moved

C You are connected to a node that does not own the slots you want to move

D The cluster is down and cannot process commands

💡 Hint

The MOVED error indicates a redirection in Redis Cluster.

The MOVED error means the command was sent to a node that does not own the requested slot, so you must connect to the correct node to reshard.

❓ optimization

expert

How to minimize downtime during resharding in a large Redis Cluster?

You have a large Redis Cluster and want to reshard hash slots with minimal downtime. Which approach is best?

A Stop all clients, move all slots at once, then restart clients

B Use the redis-cli reshard command with small batch sizes and monitor progress

C Manually edit cluster configuration files to reassign slots instantly

D Restart all nodes sequentially during resharding

💡 Hint

Think about gradual data movement and client availability.

Moving slots in small batches with redis-cli reshard allows the cluster to remain available and reduces downtime.