On: State of Clojure 2016 – Results and Analysis

[espeed]

NB: Datomic is not "append only" (when it was first released, I thought it was too):

  Note that accumulate-only is a semantic property, and is
  not the same as append-only, which is a structural 
  property describing how data is written. Datomic is not an
  append-only system, and does not have the performance
  characteristics associated with append-only systems.

Source: http://docs.datomic.com/indexes.html

[brilliantcode → espeed]

I updated my original post to reflect that but I'm still not sure what the difference is.