Discover the modern architecture of Waltti-APC, Finland's national Automatic Passenger Counting system. We have developed what we believe is the first application of differential privacy to anonymize real-time APC data, ensuring its safe use in trip planners and other passenger information systems. Additionally, we have crafted an API specification that allows new vendors to easily step into the market of onboard counting devices without prior knowledge of public transit. All open source, of course. Join us for an exploration of our data pipeline, powered by Apache Pulsar.