Lua vs transactions comparison in Redis - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start a Redis transaction.

Redis

redis.call('[1]')

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

AMULTI

BEXEC

CWATCH

DDISCARD

Attempts:

3 left

💡 Hint

Common Mistakes

Using EXEC instead of MULTI to start the transaction.

Using WATCH which is for monitoring keys, not starting transactions.

The MULTI command starts a Redis transaction block.

2fill in blank

medium

Complete the Lua script to atomically increment a key by 1.

Redis

return redis.call('[1]', KEYS[1]) + 1

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

AGET

BINCR

CSET

DDEL

Attempts:

3 left

💡 Hint

Common Mistakes

Using GET and adding 1 in Lua which is not atomic.

Using SET which overwrites the value.

The script uses INCR to atomically increment the key by 1.

3fill in blank

hard

Fix the error in the Lua script to ensure atomic increment.

Redis

local val = redis.call('[1]', KEYS[1])
if not val then
  redis.call('[2]', KEYS[1], 1)
  return 1
end
return redis.call('[3]', KEYS[1])

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

AGET

BSET

CINCR

DDEL

Attempts:

3 left

💡 Hint

Common Mistakes

Using DEL which deletes the key instead of setting or incrementing.

Using GET instead of INCR for incrementing.

The script first GETs the value. If it doesn't exist, it SETs it to 1. Otherwise, it INCRs the value.

4fill in blank

hard

Fill both blanks to watch a key and start a transaction.

Redis

redis.call('[1]', KEYS[1])
redis.call('[2]')

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

AWATCH

BMULTI

CEXEC

DDISCARD

Attempts:

3 left

💡 Hint

Common Mistakes

Using EXEC before MULTI.

Using DISCARD which cancels the transaction.

You WATCH the key to monitor changes, then start the transaction with MULTI.

5fill in blank

hard

Fill all three blanks to execute a transaction with error handling.

Redis

redis.call('[1]')
local success = redis.call('[2]')
if not success then
  redis.call('[3]')
end

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

AMULTI

BEXEC

CDISCARD

DWATCH

Attempts:

3 left

💡 Hint

Common Mistakes

Using WATCH instead of DISCARD to cancel.

Calling EXEC before MULTI.

You start the transaction with MULTI, execute it with EXEC, and if it fails, cancel with DISCARD.