Time-based event queues in Redis - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add an event with a timestamp to a Redis sorted set.

Redis

ZADD events [1] "event1"

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

AZADD

B"event1"

Cevents

D1625097600

Attempts:

3 left

💡 Hint

Common Mistakes

Using the event name as the score instead of the timestamp.

Forgetting to provide the score before the member name.

The ZADD command adds a member with a score (timestamp) to a sorted set. Here, 1625097600 is the Unix timestamp for the event.

2fill in blank

medium

Complete the code to retrieve all events with timestamps up to a given time.

Redis

ZRANGEBYSCORE events -inf [1]

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

A"event1"

B1625097600

Cnow

D+inf

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string like 'now' instead of a numeric timestamp.

Using '+inf' which would return all events regardless of time.

The ZRANGEBYSCORE command retrieves members with scores between the given min and max. Here, 1625097600 is the max timestamp to get all events up to that time.

3fill in blank

hard

Fix the error in the code to remove events older than a certain timestamp.

Redis

ZREMRANGEBYSCORE events -inf [1]

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

A1625097600

B"event1"

C+inf

D-inf

Attempts:

3 left

💡 Hint

Common Mistakes

Using a member name instead of a timestamp.

Using '+inf' which would remove all events.

The ZREMRANGEBYSCORE command removes members with scores between the given min and max. To remove old events, use the max timestamp as the cutoff.

4fill in blank

hard

Fill both blanks to add multiple events with their timestamps to the sorted set.

Redis

ZADD events [1] "event1" [2] "event2"

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

A1625097600

B"event1"

C1625184000

D"event2"

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping event names and timestamps.

Using strings instead of numeric timestamps for scores.

When adding multiple members with ZADD, each score must be followed by its member. Here, 1625097600 and 1625184000 are timestamps for event1 and event2.

5fill in blank

hard

Fill all three blanks to retrieve events within a time range and limit the number of results.

Redis

ZRANGEBYSCORE events [1] [2] LIMIT 0 [3]

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

A1625097600

B1625184000

C10

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using strings instead of timestamps for min and max.

Confusing the LIMIT count with offset.

The ZRANGEBYSCORE command can take min and max scores to filter events by time. The LIMIT clause restricts the number of results returned. Here, events between timestamps 1625097600 and 1625184000 are retrieved, limited to 10 results.