A motivation for us to move to pulp 3? or a motivation for the pulp team to work on pulp 3?
I would say largely the answer to both is the database. Mongo (surprise surprise) did not scale well when used with heavily relational data which pulp used a lot of. It required ‘joins’ to be done in memory and also made our deployment more complicated.
As part of ‘porting’ to a relational database, they took the opportunity to rethink a lot of aspects of pulp and thus the end result is quite different.
That was a discussion that was going on back then but really didn’t go anywhere. There is no elastic search in pulp 3. Pulp 3 consists of a django application, postgresql (or other relation db), RQ (a queuing system) and redis (the backend of the queuing system).