MySQLTuner : MySQLTuner is a script written in Perl that will assist you with your MySQL configuration and make recommendations for increased performance and stabi...
Use The Index, Luke! : A tutorial covering SQL indexing and SQL tuning for developers: avoiding unnecessary details about database internals.
SQL indexing is the most effect...
Minimize round-trip times : An article on the best practices to apply in order to minimize HTTP round-trip times
Blackfire : Blackfire Profiler automatically instruments your code to gather data about consumed server resources like memory, CPU time, and I/O. But Blackfire Pr...
Vitess is a database clustering system for horizontal scaling of MySQL.
Minimize round-trip times : An article on the best practices to apply in order to minimize HTTP round-trip times
Let's make the web faster : There are many ways to make websites run faster. In this section, you can discover performance best practices that real web professionals employ in th...
Mink : Mink is an open source acceptance test framework for web applications, written in PHP 5.3.
Pyramid : Pyramid is a very general open source Python web framework.
Subgraph Vega : Vega is an open source platform to test the security of web applications. Vega can help you find and validate SQL Injections, Cross-Site Scripting (XS...
Nice write-up on techniques for scaling up a web application.