The repeating problem with cloud is that it no longer stops my bad code by OOM, rather the sky is the limit for both the memory and the cost. I heard funny story about people who bought badly written code which was constantly going up through the roof with resources. They got angry with my friend, told him the software is not bad, but the hosting is (software was bought with hardware from the manufacturer) and migrated to cloud, only to meet the hard iron hammer of karma (which in this case was embodied by high bill)
Also in my opinion billing is the new perf test but post factum and obscure, i.e. it is super easy to miss some key points in the development and then wake up with the costs falling down the responsibility sink (https://news.ycombinator.com/item?id=41891694)