Modern web services run across hundreds of thousands of servers in a data center, i.e., at hyperscale. With the end of Moore's Law and Dennard scaling, successive server generations running these web services exhibit diminishing performance returns, resulting in architects adopting hardware customization. An important question arises: Which web service software operations are worth building custom hardware for? To answer this question, we comprehensively analyze important Facebook production services and identify key acceleration opportunities. We then develop an open-source analytical model, Accelerometer, to help make well-informed hardware decisions for the acceleration opportunities we identify.