Josh Hesketh developed the histogram_stddev function for the streaming PromQL engine in the grafana/mimir repository, enabling precise standard deviation calculations for native histograms across multiple schema types. He implemented robust handling for schema variations and edge cases, ensuring the function’s reliability in diverse monitoring scenarios. The work included comprehensive testing to validate correctness and maintain low latency in streaming queries. Josh integrated the new function into the existing evaluation paths and updated the function registry, leveraging his expertise in Go, histogram data structures, and statistical calculations. This enhancement supports more accurate metric analysis and monitoring within the streaming query engine.