[cormacrelf]

You can do all of this with https://materialize.com, and you don’t need to write it in Java. Just connect it to a Postgres instance and start creating materialised views using SQL. These views then auto update. So much so, that you can create a view for the top 10 of something, and let it sit there as the list updates. Otherwise just use normal select statements from your views using any Postgres client.