Heat maps communicate succinctly how the distribution of a value evolves over time. Performance metrics like latency or API response time often have a complicated multimodal distributions, and summarizing them in single values like mean or 90th percentile for a visualization makes many interesting events invisible. You need to look at histograms to see the full distribution, and that’s exactly what heat maps are: histograms, plotted over time, with color intensity signalling frequency.
