Do you recommend any particular alternative to New Relic? In particular, I'd be interested in something that helps answer the questions "How much memory am I using, and what's using it?" New Relic helps a lot with the latter question, as it can aggregate request time by Rails action. E.g. it can say "30% of your Apache workers' time is spent in this one Rails action." Which helps you understand what's driving the need for more Apache workers, and thus the need for more memory.