C may have some shortcomings, particulary policing memory vioations, but can be very lightweight and very fast. Remember, Linux and Apache/NGINX are in C . Implementing the site specifics in C isn't that much of a stretch. The extra speed could even make your site that much more useable.

The canonical genome browser is written in C: http://genome.ucsc.edu/cgi-bin/hgTracks?db=hg19 ... for pure speed.