During the summer of 2020, Slack's performance infrastructure team was tasked with building a load testing solution that could simulate hundreds of thousands of users in a single team ahead of a big customer launch. What followed was two months of prototyping: figuring out the right balance between simulating high-fidelity usage, efficient usage computing resources, and speed of execution. After a momentous, successful ramp up to 500k simulated users, we kept going. We continued to build momentum, enabling the ability to test specific user flows, and ramping up to just under 2 million simulated users to see how far we could take Slack's infrastructure. Join me for a roller coaster ride of a story and a thrilling live demo of what our load testing systems can do!