Redis can be told that a key should only exist for a certain length of time. This is accomplished with the EXPIRE and TTL commands.

    SET resource:lock "Redis Demo"

    EXPIRE resource:lock 120

This causes the key resource:lock to be deleted in 120 seconds. You can test how long a key will exist with the TTL command. It returns the number of seconds until it will be deleted.

    TTL resource:lock => 113

    // after 113s

    TTL resource:lock => -2

The -2 for the TTL of the key means that the key does not exist (anymore). A -1 for the TTL of the key means that it will never expire. Note that if you SET a key, its TTL will be reset.

    SET resource:lock "Redis Demo 1"

    EXPIRE resource:lock 120

    TTL resource:lock => 119

    SET resource:lock "Redis Demo 2"

    TTL resource:lock => -1