WATCH for optimistic locking in Redis - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start watching a key for optimistic locking.

Redis

redis_client.[1]('mykey')

Drag options to blanks, or click blank then click option'

Amulti

Bwatch

Cexec

Dunwatch

Attempts:

3 left

💡 Hint

Common Mistakes

Using MULTI instead of WATCH to monitor keys.

Using EXEC before WATCH.

Using UNWATCH to start watching keys.

The watch command tells Redis to monitor the key for changes before executing a transaction.

2fill in blank

medium

Complete the code to start a transaction after watching keys.

Redis

redis_client.[1]()

Drag options to blanks, or click blank then click option'

Amulti

Bwatch

Cexec

Dunwatch

Attempts:

3 left

💡 Hint

Common Mistakes

Using WATCH instead of MULTI to start a transaction.

Using EXEC before MULTI.

Using UNWATCH to start a transaction.

The multi command starts a transaction block in Redis after watching keys.

3fill in blank

hard

Fix the error in the code to execute the transaction and release the watch.

Redis

redis_client.[1]()

Drag options to blanks, or click blank then click option'

Amulti

Bwatch

Cunwatch

Dexec

Attempts:

3 left

💡 Hint

Common Mistakes

Using MULTI instead of EXEC to run the transaction.

Using WATCH to execute commands.

Using UNWATCH before executing the transaction.

The exec command executes all queued commands in the transaction and releases the watch.

4fill in blank

hard

Fill both blanks to unwatch keys and discard the transaction.

Redis

redis_client.[1]()
redis_client.[2]()

Drag options to blanks, or click blank then click option'

Aunwatch

Bdiscard

Cexec

Dmulti

Attempts:

3 left

💡 Hint

Common Mistakes

Using EXEC instead of DISCARD to cancel the transaction.

Using MULTI instead of UNWATCH to stop watching keys.

Not calling UNWATCH before DISCARD.

UNWATCH stops watching keys without executing the transaction, and DISCARD cancels the transaction queue.

5fill in blank

hard

Fill all three blanks to watch a key, start a transaction, and execute it.

Redis

redis_client.[1]('counter')
redis_client.[2]()
redis_client.[3]()

Drag options to blanks, or click blank then click option'

Awatch

Bmulti

Cexec

Dunwatch

Attempts:

3 left

💡 Hint

Common Mistakes

Skipping WATCH before MULTI.

Using UNWATCH instead of EXEC to run the transaction.

Calling EXEC before MULTI.

First, WATCH monitors the key. Then, MULTI starts the transaction. Finally, EXEC runs the queued commands.