Who has heard of or knows what a key value pair is? How about epoch time or unix time? Then you can use graphite.
Ceres does not use space for time periods which contain no datapoints, uses 33% less disk space, able to store the datapoints for a single metric across multiple servers. Dashboard trunk: Save graphs drag'n'drop reordering & merging graphs, all the composer features are there (graph options, functions, etc) plus a few more (breakout a graph with wildcards into separate graphs,