Better site and database performance I'm working on a Drupal community site and I want to ask about these things:


How do I make a Drupal site more secure?
How do I make my site work as fast as possible when there is a lot of visitors and users on the site, and there is a lot of interaction with the database at the same time? How do I maintain the database consistent in this situation?
How do I configure Drupal to work during high server load? How do I configure my server's hardware to work during high load moments?
1 - Use captchas and spam filtering; Mollom is a good place to start. There is also  info on hardening Drupal in the drupal handbook, ie. http://drupal.org/writing-secure-code.

2 - For starters, turn on the performance module that comes with Drupal.

3 - This is a big question. I have heard good things about Context HTTP Headers, a module contributed by the White House Drupal team. You can find a comparison table on Caching: Moduls that make Drupal scale.