At Uber, speed and responsiveness of our mobile apps is of critical importance. At the same time, measuring and tuning mobile app performance brings many unique challenges, due to a huge variety of device capabilities and network conditions, differences in compilers and runtimes, and a large number of mutually-interacting external libraries and frameworks. In this talk, I will discuss some of these challenges, and present how our group is using static and dynamic analysis and custom optimizations to address them.