SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '247df237a452341af4ba8adaa95b5338493dbd3a24d5665fcd831581c2515a9c' 
  AND token = 'KsxmXOtkAjVQovXffBYe4IT+enLzUZ/EH08MWotaca0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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