Let's profile new pride of the Magento Inc. — The best of the class eCommerce version 2.4.0
I don’t have time profile and test everything however I have installed M2.4 without any data. Let's compare it with a production website.
We can test only FPC how it works and what issues in M2.4 we have.
Magento 2.4 cached page generation time.
Result: 136 ms.
Magento 2.4 has some core issue there
PHP 7.4 function mdecrypt_generic is slow
Production 2.3.5 Website profile
Cached page generation time: 35ms
Magento 2.4 is 3–4 times slower