I don't know if there is a good write-up on it but the APR Apache Portable Runtime Library 1.6 to 1.7 rewrite / refactor that allowed the performance of Apache

I don't know if there is a good write-up on it but the APR Apache Portable Runtime Library 1.6 to 1.7 rewrite / refactor that allowed the performance of Apache to be on par with NGinx at the time I would call a successful major software rewrite or refactor. (Apache 2.2.x to Apache 2.4.x) The changes in performance were a night-and-day difference especially in combination with mpm-event.