What observability stack replaced Prometheus+Grafana at your org?

We've been running Prometheus + Grafana for 3 years. It works but the cardinality explosion from k8s labels is becoming unmanageable. Alerts are noisy, retention is painful, and our SRE team spends more time maintaining the stack than acting on it. Looking for real-world experience: - Did you migrate to Grafana Mimir, Thanos, VictoriaMetrics, or something cloud-native (Datadog, New Relic, Honeycomb)? - What was the migration path? Did you run both stacks in parallel? - How did you handle historical data retention during the switch? - Any gotchas with PromQL compatibility? Team size: 12 engineers, 200+ nodes, ~2M active time series. Budget is not the primary constraint — operational overhead is. Jurisdiction: N/A.