SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '311149fc80a54f4e91a18635d91e6cf7a85b0c633f626e4343738eaa79fd1a55' 
  AND token = 'dPnVfaiqXKSv9Pn+xfDm9vGNhkAwlMSrW+Vigya6Tk4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00014

JSON explain

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