The District's phone and online system crashed on Thursday morning just as thousands of residents became newly eligible to sign up for 4,350 appointments for the COVID-19 vaccine. Mayor Muriel Bowser said this week that appointments would open at 9 a.m. to residents living in priority ZIP codes who are 65 or older, are 18 and older and have a qualifying medical condition ranging from asthma to cancer, or work in a number of essential jobs from child care to grocery stores. But the demand almost immediately overwhelmed the city's online and phone system, with many callers reporting that they couldn't even get through on the phone. Others reported that even when they did get through online, the system wasn't updated to reflect the new eligibility criteria for pre-existing conditions and essential workers. https://dcist.com/story/21/02/25/dc-vaccine-appointment-system-crashes-qualifying-medical-conditions/ Testing scalability—why bother? That's what customers are for.