Ruby memory, ActiveRecord and Draper

At Appaloosa we often process CSV. When we process thousands of CSV lines of users that need to be added to (or removed from) a group, we are seeing a huge increase in memory. Sometimes the Heroku dynos cannot manage it. We will explain how we jump from this when processing 4_000 users (look at blue line but also time): memory profilerWe used stackprof, memory_profiler. We look at tool like speeds