PromCon Online 2021, a virtual event held on May 3 as part of KubeCon + CloudNativeCon, focused on the Prometheus monitoring system and featured contributions from the Grafana Labs team among thousands of Prometheus users. Highlights included Grafana Labs' Director of Community Richard Hartmann discussing efforts to make the Prometheus community more open, Peter Å tibraný explaining the conversion of Cortex data to TSDB blocks, and Tom Wilkie exploring the future of Prometheus remote write. Additionally, Björn Rabenstein presented improvements in Prometheus histograms, and Atibhi Agrawal offered insights into new matchers in Prometheus Alertmanager. The event marked Grafana Labs' transition from contributing to Cortex to launching Grafana Mimir, a scalable long-term storage solution for Prometheus, capable of managing over a billion metrics.