Kinda. PHP is fine for web workloads. Don't forget Facebook tried to move off PHP and wrote Hack/HHVM because of the performance. It just happens that PHP 7 was faster.
I've not looked at the codebase, but there are probably some routines (search) that could be done faster outside pure PHP/Postgres.
The dev seems to have done a pretty good job with this though, performance issues are likely server load more than the stack. Not sure what he's running this on...