ArangoDB is an incredible database with some very shy marketing imo - edge indexing over json documents is too good of a sweet spot.
Not sure if still actual, however among headaches I remember race conditions in the node driver(rocksdb engine) and maybe less straightforward clustering (compared to Couchbase/Cassandra/etc at least).
The race conditions have been eliminated and we greatly simplified the cluster setup.
With this "new" tool shipped with arangodb https://github.com/arangodb-helper/arangodb it is just a single line on each machine to get the cluster up and running.
Not sure if still actual, however among headaches I remember race conditions in the node driver(rocksdb engine) and maybe less straightforward clustering (compared to Couchbase/Cassandra/etc at least).