What does redis expiration time mean?

Redis expiration time allows setting a duration for the key after which the key and its value will be deleted. (1) Set the expiration time through the EXPIRE or PEXPIRE command. (2) Expiration time helps to free up storage space, avoid data obsolete, and manage queues. (3) You can use the TTL command to obtain the expiration time, and the PERSIST command cancels the expiration time.

Redis expiration time

The expiration time of Redis is the duration when a key remains active in the Redis database. Once the expiration time is reached, the key and its associated values ​​will be deleted from the database.

Set expiration time

The expiration time can be set for the key through EXPIRE or PEXPIRE command:

• EXPIRE: Set the expiration time in seconds.
• PEXPIRE: Set the expiration time in milliseconds.

For example, to set the key "my_key" to expire after 60 seconds, you can use the following command:

 <code>EXPIRE my_key 60</code>

The role of expiration time

Expiration time is very useful for managing data in Redis databases because it can:

• Free up space: Automatically delete no longer needed keys, thus freeing up space in the Redis database.
• Avoid data obsolete: Expiration time can help avoid data obsolete because once the key expires, it will be deleted from the database.
• Queue Management: You can use expiration time to manage queues, such as delay queues or priority queues.

Get expiration time

You can use the TTL command to get the remaining expiration time of the key:

 <code>TTL my_key</code>

If the returned value is -1 , it means that the key has not set an expiration time.

Cancel expiration time

The expiration time of the key that can be cancelled through the PERSIST command:

 <code>PERSIST my_key</code>

Once the expiration time of the key is cancelled, it will remain active until manually deleted.

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