Rendering
With tens of thousands of seats, DOM- and SVG-based approaches became too slow. Moving the seat map to WebGL with custom shaders kept selection and zooming at 60 fps, also on phones.
Load peaks
Popular events cause sharp traffic spikes when sales open. A Kafka-based work queue handles long-running jobs and absorbs these peaks; business events and logs go to ELK.
Further work
Sales analytics dashboards backed by ClickHouse, with a generic filter system that supports nested logical operations — and frontend performance improvements measured with Sentry.