SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2a312e368547941e1eed4df164076e8f879b9163936ad85d85cd05951de25ccc' 
  AND token = 'b75IfpvcCVubWxeBLzaN3iCEDpP960iIrBwj/ESf5Yw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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