We have received some great questions for our ASK JOHN feature and narrowed these down to a few questions, here are your answers straight from the source!
Scalability and speed
How should we upgrade our server as our community increases in size?
To scale your site the first thing to do would be to split the web server and database servers. After that, you can drop in a separate memcached server. You can also use multiple web servers behind a load balancer, however some features of the admin panel will not work correctly. It is possible to scale the database using mysql-proxy, however you must use Engine_Db_Adapter_Mysql. Due to the complexity and variation of each server we recommend hiring 3rd party developers.
Shaun has written an excellent article on tips to increase speed. In particular: Make sure the site is in production mode and install APC, these will provide significant speed improvements.
What is the best method for extending core features of SE without losing upgradeability?
It is recommended that you keep a record of the files you modify and backup the customized files. While upgrading you will be shown a list of files which may be overwritten. After the upgrade process, add your customizations to the files. Please note that upgrades do not preserve customizations.