I would like to share what I've learned while working on Basic RUM - an open source Real User Monitoring system. I combined a few open source projects (Grafana, ClickHouse, Traefik and Boomerang JS) and I was able to build a data pipeline that processes web performance metrics and visualises trends which helps webmasters to understand the performance metrics. During the talk I would like talk about the internals of a RUM system, to stress on the performance data handling, why I've chosen ClickHouse as timeseries database, why I've chosen Grafana as a visualisation platform and how all the components of the system are related.