Why phpseclib takes time in magento 2.3.3?

Question

Recently we have upgraded Magento 2.2.8 to 2.3.3 and PHP 7.2.11, post that we are facing more performance issues. When we put site in maintenance mode phpseclib related changes keep takes time.

We are not sure why this phpseclib taking more time. in PHP 7.1 we didn't have this issue. mcrypt won't be there in PHP 7.1. Whether PHP 7.2 has any specific issues in Magento 2.3.3?

Answer 1

As you noted, mcrypt isn't installed, thus mcrypt_compat is being used. mcrypt_compat will use OpenSSL if it's available so my best guess is (1) you don't have OpenSSL installed or (2) you're using an algorithm OpenSSL doesn't support, like rijndael-256 (which would mean mcrypt_compat is having to use a pure-PHP implementation of rijndael-256, which is invariably going to be slower).