Advanced Aggregates is one of the modules that I consider indispensible in Drupal 7. With the (then upcoming) release of Drupal 8, I was really missing it in my projects (especially the At One website which I was wanting to be performant in public situations). There was no current port in progress, so the logical solution seemed to be talk to Mikeytown (the AdvAgg creator). Now a minimal AdvAgg has been functional for months (with occasional breaks as more features are ported) and the full release is coming quite soon (probably early February 2016).
All credit of course to Mikeytown and all the helpful past and future contributors. Any bugs in the Drupal 8 port are almost certainly mine as it was a significant rewrite due to the large scale API and backend changes in Drupal 8.