Listings with mixed privacy
If you go to explore, search or pretty much any given listing, you may encounter that the system enables to list content aware of the private content if you have access to it. This may look as a neat feature, but is very expensive to carry specially with larger collections. Problem is that each user ask the database for a different list so imagine the load of an album with 20,000 pictures and the impact of just a couple of users listing contents.
Even with cache, the problem is that the listing job is too expensive if each user requires its own version of it. This is very similar to the effect of having NSFW flagging everywhere, it compromises the listing performance. Fortunately, we can get rid of this by simply stop making mixed listings and having a place for the public, a place for the private.