Read-only replicas in Redis - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of this Redis command on a read-only replica?

Consider a Redis read-only replica. What will be the result of running the command SET key1 value1 on this replica?

Redis

SET key1 value1

A Error: command not found

B OK

C nil

D READONLY You can't write against a read only replica.

💡 Hint

Think about what a read-only replica is designed to do.

A read-only replica in Redis does not allow write commands like SET. It returns an error message indicating the command is not allowed.

🧠 Conceptual

intermediate

Why use read-only replicas in Redis?

Which of the following is the main reason to use read-only replicas in Redis?

A To increase write throughput by distributing writes

B To provide high availability and distribute read load

C To encrypt data automatically

D To store backup data that is never accessed

💡 Hint

Think about how replicas help with scaling and availability.

Read-only replicas help by allowing many clients to read data without overloading the main server, improving availability and read performance.

📝 Syntax

advanced

Which command correctly configures a Redis instance as a read-only replica?

You want to configure a Redis server as a read-only replica of a master at IP 192.168.1.10 port 6379. Which command should you run on the replica?

A REPLICAOF 192.168.1.10 6379

B SLAVEOF 192.168.1.10 6379

C MASTEROF 192.168.1.10 6379

D FOLLOW 192.168.1.10 6379

💡 Hint

The newer Redis versions use a different keyword than SLAVEOF.

The correct command to configure a replica is REPLICAOF. SLAVEOF is deprecated but still works in older versions.

❓ optimization

advanced

How to optimize read performance using Redis replicas?

You have a Redis master and multiple read-only replicas. Which approach best optimizes read performance for many clients?

A Send all read and write requests to the master only

B Send all requests to a single replica to reduce network hops

C Distribute read requests evenly among replicas, write requests to master

D Disable replicas and use only the master for all operations

💡 Hint

Think about load balancing reads and writes.

Distributing read requests among replicas reduces load on the master and improves read throughput.

🔧 Debug

expert

Why does this Redis replica not replicate writes from master?

A Redis replica is configured with REPLICAOF 10.0.0.1 6379. However, writes made on the master do not appear on the replica. What is the most likely cause?

A Network connectivity issues prevent replication

B The master has disabled replication with the replica

C The replica is in read-only mode and cannot replicate writes

D The replica was started with the --slave-read-only no option

💡 Hint

Replication requires network communication between master and replica.

If writes do not appear on the replica, network issues are the most common cause preventing replication.