SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9d6c66d999f7129552d816000def950090168bfaa504804dc28043ba57f18cc' 
  AND token = 'USOfN18xXAhLjuLK6joo0TGqHvhkkvZY33KkyHoZ9OA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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