Novice observability practitioners are often overly obsessed with performance. They might approach instrumentation with skepticism and have concerns about latency degradation or resource consumption. This talk is a primer on the topic of instrumentation overhead, and it will teach you how to think about overhead in an observability context. We will cover the causes of overhead and why overhead is so hard to measure and even harder to predict reliably. Lastly, we will present some practical techniques for understanding overhead in your environment and some strategies for coping with it.