public function createTtlIndex(int
$expireAfterSeconds = 0
) { $this->
getCollection()->
createIndex( [ // key
'expires_at' => 1,
],
[ // options
'expireAfterSeconds' =>
$expireAfterSeconds,
] );
} /**
* @return void
*
* @throws LockExpiredException when save is called on an expired lock
*/