Down sampling is an extremely common operation used when plotting time-series data on graphs when there is too much data to get a good looking/meaningful graph. This would pick and choose "important" data points based on an algorithm such as "Largest-Triangle-Three-Buckets" (https://skemman.is/bitstream/1946/15343/3/SS_MSthesis.pdf) instead of returning the entire data set.

Not only would this make prettier graph but it will also reduce the overall payload returned from the data thus reducing network related latency.

This would be an awesome addition to timeseries!