The first comment is from the Cofounder and he lists the _features_ that motivated a rewrite:

>Then there's the question of why we did a rewrite at all. We wanted to get at some important requirements: >Unlimited cardinality >Analytics queries against time series at the performance of a columnar DB >Use object store as the durability layer for historical data (i.e. separate compute from storage) >SQL and broader ecosystem compatibility >All of that stuff taken together meant that we'd be rewriting most of the core of the database. ...