How can I view and handle expired keys in Redis?

Redis offers several commands for viewing and managing expired keys.

1. You can use the TTL command to view the remaining time to live of a key. The command is used as follows:
2. Time to Live key
3. Return value:
4. If the key exists and has a set expiration time, the remaining time of the key’s survival will be returned in seconds.
5. If the key does not exist, return -2.
6. If the key exists but has not been set with an expiration time, -1 is returned.
7. The PTTL command can be used to check the remaining time to live of a key in milliseconds. To use the command:
8. Primary Through the Lens (PTTL) key
9. The return value is the same as the TTL command, except the returned time is in milliseconds.
10. The EXPIRE command can be used to set an expiration time for a key. The command is used as follows:
11. The key will expire in a specific amount of seconds.
12. The parameter “seconds” is an integer that represents the expiration time (in seconds) of the key. Once the expiration time is reached, the key will be automatically deleted.
13. The PERSIST command can be used to remove the expiration time of a key, making it permanent. The command is used as follows:
14. Keep the key
15. When the expiration time of a key is successfully removed, the command returns 1; when the key does not exist or does not have an expiration time set, the command returns 0.
16. The “KEYS” command can be used to retrieve all keys that match a specified pattern. The format for using the command is:
17. Pattern of keys.
18. The parameter pattern can use wildcard characters to match patterns of keys, for example, * matches any number of characters, and ? matches one character.

Please be cautious when using the KEYS command in a production environment as it will iterate through the entire key space and may impact performance. In production environments, it is recommended to use the SCAN command for a gradual iteration through keys.