Why long ttfb?

Question

Nginx

There is a site multiblender.ru. costs nginx + apache + mysqli + php5. The site has a very long ttfb(from 2 sec) which is very bad. With the load of search bots, the loading of the site increases to 20 or more seconds. Before that, the site was on apache and everything was working fine.
Hardware
2хIntel(R) Atom(TM) CPU C2750 @ 2.40GHz
2GB ram
50GB SSD
What can be tweaked to get rid of apacha and choose another solution?

Answer 1

apache is definitely an extra link here.
Well, see what slows down nginx, php or mysqli
(in nginx you can see $upstream_response_time and in mysql enable slow query log )

Answer 2

Measure ttfb for static, system load, memory, io.
Then I would start by profiling a copy of the site in a virtual machine.
Be sure to remove Apache - it is definitely superfluous.
There are many useful recipes for combining ttfb nginx, but this is unlikely to be the cause of the problem, I think the problem is in the site itself.