SET with expiry (EX, PX) in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the EX option do in the Redis SET command?

The EX option sets the expiration time for the key in seconds. After this time, the key will be automatically deleted.

beginner

How is PX different from EX in the Redis SET command?

PX sets the expiration time in milliseconds, while EX sets it in seconds.

beginner

Write a Redis command to set key 'session' with value 'abc123' that expires in 10 seconds.

SET session abc123 EX 10

intermediate

What happens if you set a key with SET and an expiry, and then set it again without expiry?

The key will be updated with the new value and the expiry will be removed, so it will not expire unless set again.

intermediate

Can you use both EX and PX options together in a single SET command?

No, you can only use one expiry option at a time: either EX (seconds) or PX (milliseconds). Using both will cause an error.

What unit of time does the EX option use in Redis SET command?

A Milliseconds

B Minutes

C Seconds

D Hours

EX sets the expiration time in seconds.

Which Redis SET option sets expiry in milliseconds?

A PX

B EX

C NX

D XX

PX sets the expiration time in milliseconds.

What happens if you set a key with SET and EX 5, then set it again without expiry?

A The key keeps the original expiry

B The command fails

C The key expires immediately

D The key expiry is removed

Setting a key again without expiry removes any previous expiry.

Can you use both EX and PX options together in one SET command?

A No, it causes an error

B Yes, to set two expiries

C Yes, PX overrides EX

D No, but it sets the longer expiry

Using both EX and PX together causes an error.

Which command sets key 'token' with value 'xyz' to expire in 500 milliseconds?

A SET token xyz EX 500

B SET token xyz PX 500

C SET token xyz EX 0.5

D SET token xyz PX 5

PX 500 sets expiry to 500 milliseconds.

Explain how to set a key with an expiration time in Redis using the SET command.

Think about how you tell Redis to delete a key automatically after some time.

What happens if you set a key with expiry and then overwrite it without expiry? Why is this important?

Consider what happens to the timer when you update the key without expiry.