SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c1554c13c3dfc48e295439f7e86bbb3afea51709e868b5b9990004d5c4196c9' 
  AND token = 'LBQfwo/ThiUemVbrBZiJltgU9IkpYRkLCSvys7V5/Y8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}