SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81be10daacfcec7219ca47317e1b4563d0daced9d61467d8dedf98b338de65d6' 
  AND token = 'KcKobjeURk1SHqKgYBI7fr3XsANVWT5mtMHb/avV4gE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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