Every AWS bill tells a story. After couple of years as a DevOps engineer reviewing cloud infrastructure, I've learned to read that story, and it almost always has the same five chapters. These aren't exotic edge cases. They show up on the bills of well-run teams with experienced engineers. They survive because cloud billing is complex, everyone is busy, and "we'll optimise later" is the most expensive phrase in engineering. Here's what to look for — and exactly how to fix each one. 1. Dev/Staging RDS Running 24/7 What it costs: A db.r5.xlarge running continuously costs ~$876/month. If it's only used 8 hours a day on weekdays, you're paying for 720 hours and using ~170. Why it happens: The database got created for a sprint, the sprint ended, and nobody scheduled a shutdown.…