Multi-key transactions for consistency in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a multi-key transaction in Redis?

A multi-key transaction in Redis is a way to execute multiple commands on different keys as a single atomic operation, ensuring all commands succeed or none do.

beginner

Which Redis commands start and execute a multi-key transaction?

The MULTI command starts a transaction, and EXEC executes all queued commands atomically.

intermediate

How does Redis ensure consistency when multiple keys are involved in a transaction?

Redis queues all commands after MULTI and runs them together with EXEC. If any watched key changes, the transaction aborts to ensure consistency.

intermediate

What role does the WATCH command play in multi-key transactions?

WATCH monitors one or more keys for changes. If any watched key changes before EXEC, the transaction aborts to prevent inconsistent updates.

advanced

Can Redis transactions be rolled back automatically if a command fails?

No, Redis transactions do not support automatic rollback. All commands are queued and executed atomically, but if a command fails during execution, previous commands are not undone.

Which command starts a multi-key transaction in Redis?

A EXEC

B MULTI

C WATCH

D DISCARD

MULTI starts the transaction by queuing commands.

What happens if a watched key changes before EXEC is called?

A Redis automatically retries the transaction

B The transaction continues normally

C The transaction aborts and EXEC returns null

D The watched key is reset

If a watched key changes, Redis aborts the transaction to avoid inconsistent updates.

Which command executes all queued commands in a Redis transaction?

A EXEC

B DISCARD

C WATCH

D MULTI

EXEC runs all commands queued after MULTI atomically.

Can Redis transactions include commands on multiple keys?

A Yes, Redis supports multi-key transactions

B No, transactions are limited to one key

C Only if keys are in the same hash slot

D Only with Lua scripts

Redis transactions can include commands on multiple keys, executed atomically.

What does the DISCARD command do in Redis transactions?

A Starts watching keys

B Executes the queued commands

C Locks keys for the transaction

D Cancels all queued commands and ends the transaction

DISCARD cancels the transaction and clears queued commands.

Explain how Redis uses MULTI, EXEC, and WATCH commands to maintain consistency in multi-key transactions.

Think about how Redis prevents conflicts when multiple clients update keys.

Describe the limitations of Redis transactions regarding rollback and error handling.

Consider what happens if a command inside EXEC fails.