Key expiry for memory management in Redis - Mini Project: Build & Apply

Key Expiry for Memory Management in Redis

📖 Scenario: You are managing a Redis database that stores temporary session data for an online store. To keep the database clean and efficient, you want to set expiration times on keys so that old sessions are automatically removed.

🎯 Goal: Build a Redis setup where you create keys for user sessions, configure expiration times, and verify that keys expire as expected to manage memory effectively.

📋 What You'll Learn

Create keys representing user sessions with specific values

Set expiration time on these keys using Redis commands

Check the remaining time to live (TTL) for keys

Demonstrate automatic key expiry after the set time

💡 Why This Matters

🌍 Real World

Setting key expiry helps automatically remove old or unused data, keeping the Redis database efficient and saving memory.

💼 Career

Many jobs require managing cache or session data with automatic expiry to ensure performance and resource management.

1

Create session keys in Redis

Use the Redis SET command to create three keys named session:user1, session:user2, and session:user3 with values data1, data2, and data3 respectively.

Redis

# Use SET commands to create session keys
# Your code here

Need a hint?

Use the SET command followed by the key name and value.

2

Set expiration time for session keys

Use the Redis EXPIRE command to set an expiration time of 60 seconds on the keys session:user1 and session:user2.

Redis

SET session:user1 data1
SET session:user2 data2
SET session:user3 data3
# Use EXPIRE commands to set 60 seconds expiry on session:user1 and session:user2
# Your code here

Need a hint?

The EXPIRE command takes the key name and the time in seconds.

3

Check the time to live (TTL) for session keys

Use the Redis TTL command to check the remaining expiration time for the keys session:user1, session:user2, and session:user3.

Redis

SET session:user1 data1
SET session:user2 data2
SET session:user3 data3
EXPIRE session:user1 60
EXPIRE session:user2 60
# Use TTL commands to check expiry time for session:user1, session:user2, and session:user3
# Your code here

Need a hint?

The TTL command shows how many seconds remain before the key expires. If the key has no expiry, it returns -1.

4

Verify automatic key expiry

Wait for 60 seconds and then use the Redis EXISTS command to check if the keys session:user1, session:user2, and session:user3 still exist.

Redis

SET session:user1 data1
SET session:user2 data2
SET session:user3 data3
EXPIRE session:user1 60
EXPIRE session:user2 60
TTL session:user1
TTL session:user2
TTL session:user3
# After 60 seconds, use EXISTS commands to check if keys still exist
# Your code here

Need a hint?

The EXISTS command returns 1 if the key exists, 0 if it does not.