Developed and integrated the histogram_stddev function into the streaming PromQL engine within the grafana/mimir repository, enabling precise standard deviation calculations for native histograms across multiple schema types. The implementation in Go focused on robust handling of histogram data structures and statistical calculations, ensuring accurate results even in edge cases. Comprehensive tests were added to validate the function’s reliability across schema variations, and the function registry along with streaming evaluation paths were updated to minimize latency impact. This work enhanced the streaming query engine’s ability to support more accurate monitoring and alerting for histogram-based metrics in production environments.