Technologies to Consider

1. MySQL Slow Query Log - to get mysql to write every queries that take over a certain amount of time
2. XHProf - Profiling with XHProf - See where the performance issues are
3. Redis - cache queries so that the performance hit of database query is not paid a second time.
4. Load Testing with Seige + monitoring with Appneta Traceview (or as an alternative New Relic or App Dynamics)
5. Continous Integration - (Jenkins, Travis, phpUnderControl, PHPCI, CircleCI etc.)
6. Automated Testing - Codeception (Acceptance and Unit Tests)
7. PHP7
8. Use Git - /w pull requests - so that code is reviewed before being pushed up - (another person is in charge of ensuring that the
functionality works & is refactored & tests present before making it into the code base)
9. SASS
10. Docker
11. React - as a pilot project for the client facing app - and if it works well then in the future into the full app
12. Gzip .css + .js + images across && minification (of js and css) 
    (https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-mod_deflate-on-centos-7
     http://stackoverflow.com/questions/31516074/how-to-enable-gzip-compression-in-yii2)