Priority queue pattern in Redis - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add an item with a priority to a Redis sorted set.

Redis

ZADD tasks [1] "task1"

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

Atasks

B"task1"

CZADD

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the member before the score

Using the key name as the score

The ZADD command adds an item with a score (priority) to a sorted set. Here, 1 is the priority score.

2fill in blank

medium

Complete the code to get the highest priority item from the Redis sorted set.

Redis

ZRANGE tasks [1] [2] WITHSCORES

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A1

B0

C-1

D-2

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 0 returns the lowest priority item

Using positive indexes to get the last element

ZRANGE with start and stop as -1 returns the last element, which has the highest score (priority) in ascending order.

3fill in blank

hard

Fix the error in the code to remove the highest priority item from the sorted set.

Redis

ZREM tasks [1]

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

A"task1"

BZRANGE tasks -1 -1

CZPOPMAX tasks

DZREM tasks -1

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to remove by index or command instead of member name

Using ZREM with a negative index

ZREM removes a member by name. You must specify the member's name, not a command or index.

4fill in blank

hard

Fill both blanks to atomically pop the highest priority item from the sorted set.

Redis

ZPOPMAX [1] [2]

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

Atasks

B1

C0

Dtask1

Attempts:

3 left

💡 Hint

Common Mistakes

Using member name instead of key as first argument

Using 0 as count which pops nothing

ZPOPMAX removes and returns the highest score members. The first argument is the key, the second is the count of items to pop.

5fill in blank

hard

Fill all three blanks to add a task with priority, then get and remove the highest priority task.

Redis

ZADD [1] [2] "task2"
result = ZPOPMAX [3] 1

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

Atasks

B5

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using different keys for add and pop

Using a string instead of a number for priority

First, ZADD adds "task2" with priority 5 to the sorted set named "tasks". Then, ZPOPMAX removes and returns the highest priority task from the same set.