Cardinality estimation Probabilistic linear HyperLogLog http://highscalability.com/blog/2012/4/5/big-data-counting-how-to-count-a-billion-distinct-objects-us.html Approximate histograms and quantile sketches with Sketch data structures DDSketch UDDSketch https://www.datadoghq.com/blog/engineering/computing-accurate-percentiles-with-ddsketch/ https://dotat.at/@/2022-07-15-histogram.html