When building a large enough set of services using node.js, there will be a point when you find that your application is suffering from performance or memory issues. When this happens, you have to roll up your sleeves, get your tools and start digging. This talk explains how you can use tools such as ab, flame graphs, heap snapshots and Chrome's memory inspector to find the cause of these. We will go over two real life issues, a CPU bottleneck and a memory leak, we found while building our services at Auth0, and also explain how we fixed them.