Tuning legacy apps could be very expensive; an application with more than 50,000 lines of code is costly to change. We need to figure out more pragmatic ways to tune them. First, we need ways to measure performance. Otherwise, we cannot prove that suggested changes are improving performance. Using nightly builds and building performance test suites help in measuring and monitoring performance. Use of caching and tuning garbage collection are cheaper “across the board” ways to improve performance. Tuning newer apps is different, and although there are ways to fix ActiveRecord performance and optimize the code, caching does not come for free.