I much appreciated the article. And even more when I discovered from other commenters that http://www.aosabook.org is a collection of architectural description of a lot of Open-Source projects. I immediately read about sendmail by Eric Allman (http://www.aosabook.org/en/sendmail.html) and I appreciated it actually more than the article about Nginx. There is a lot of wisdom in it and now I understand the reasons for some architectural decisions that have been taken for sendmail.