The upcoming Erlang/OTP 21 release will come packed with exciting features. One of them is the long awaited improvement of IO scalability (think of network sockets and file descriptors). This talk will describe what a poll set is and how it can be a bottleneck. We will see how to measure the impact of the upcoming improvements with an example on a real-world system and discover what scenarios one might benefit from them. OBJECTIVES Get a better understanding of poll sets. More details here: https://codesync.global/speaker/peter-goemoeri/