Virtually unknown is the YAWS server written in Erlang.
It runs in low memory environments long after Apache has died under heavy loads as demonstrated here:
https://www.sics.se/~joe/apachevsyaws.html
I have been running a Dokuwiki Farm with YAWS for about a year now with no issues.
Only notable configuration change to get Dokuwiki working with YAWS is redirect in fpm-php/php.ini needs set to zero as tho it is an ISS server.