MULTI command to start in Redis - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output after starting a transaction with MULTI?

You run the command MULTI in Redis to start a transaction. What is the immediate output you receive?

Redis

MULTI

A :1

B +OK

C -ERR wrong number of arguments for 'multi' command

D $-1

💡 Hint

Think about what Redis replies when a command is accepted successfully.

The MULTI command replies with +OK to indicate the transaction block has started successfully.

🧠 Conceptual

intermediate

What happens to commands after MULTI is called?

After you run MULTI, what happens to the commands you send before calling EXEC?

A Commands are queued and not executed immediately.

B Commands execute immediately and their results are returned.

C Commands are discarded until EXEC is called.

D Commands cause an error until EXEC is called.

💡 Hint

Think about how transactions work in Redis.

After MULTI, commands are queued and only executed when EXEC is called.

📝 Syntax

advanced

Which command sequence correctly starts and executes a transaction?

Choose the correct sequence of Redis commands to start a transaction, set a key, and execute the transaction.

A

MULTI
SET key1 value1
EXEC

B

EXEC
MULTI
SET key1 value1

C

SET key1 value1
MULTI
EXEC

D

MULTI
EXEC
SET key1 value1

💡 Hint

MULTI must come before queuing commands, and EXEC must come last.

The correct order is to start with MULTI, queue commands, then call EXEC to run them.

🔧 Debug

advanced

Why does this transaction fail to execute commands?

You run these commands: MULTI EXEC SET key1 value1 What is the problem?

A MULTI command was not recognized.

B EXEC must be called before MULTI.

C SET command syntax is incorrect.

D SET command is sent after EXEC, so it is not queued or executed in the transaction.

💡 Hint

Consider the order commands must be sent in a transaction.

Commands must be queued between MULTI and EXEC. Here, SET is after EXEC, so it is executed outside the transaction.

❓ optimization

expert

How does using MULTI improve Redis command execution?

What is a key benefit of wrapping multiple commands inside MULTI/EXEC in Redis?

A Improves network speed by compressing commands.

B Automatically retries commands on failure.

C Ensures all commands execute atomically without interference from other clients.

D Allows commands to execute in parallel on multiple threads.

💡 Hint

Think about what atomicity means in transactions.

MULTI/EXEC ensures all commands run as a single atomic operation, preventing partial execution.