The company I worked for a couple of jobs ago used to host approximately 130-140 java based web applications, all using Spring, on just 4 servers (primarily hosted on 2 of those) With only a few exceptions the java webapp was configured for a 256MB heap. Devs followed good practices to avoid creating excess garbage, and kept the number of libraries down to a minimum.

They also struck a good balance between doing transformations in-memory, and on the database side.

side note: There was _one_ web app that we had to host that wasn't developed in-house. It was absolutely god-awful, badly scaling, websphere based crap (I have no idea if Websphere is crap, but that application sure was bloated and underperforming). Websphere was irritating to deal with. What they did with it was worse. We eventually got the source code from them so we could fix it up, after a bunch of legal wrangles. They had 4 different custom created ORMs in it, each clearly developed by a different dev. Then for reports they never used the ORM, instead they'd make a "one query spits out the final report" query. Those queries would often be 30 - 40 subselects deep. `SELECT thing FROM foo WHERE bar in (SELECT bars IN monkey WHERE ....` and so on down the line.