Serverless FinOps: Why Lambda Cost Models Break Every Assumption You Learned from VMs Most engineering teams learn cloud cost management on VMs. You pay for uptime. You right-size vCPUs and RAM. You shut down idle instances at night. That mental model is correct for EC2 and Azure VMs. It is completely wrong for Lambda. When a team moves to serverless and applies VM intuition, they consistently over-provision memory, add Provisioned Concurrency "just in case," and miss the actual optimization levers. We have seen this pattern across teams that migrated to Lambda without updating how they think about cost. The bill does not go down. It goes sideways in ways that are hard to explain. This piece covers the real billing math, the memory-speed paradox, the cold start trap, and the framework we use to decide when Lambda wins and when a small VM is cheaper. The Billing Unit Shift That Changes Everything A VM charges for time.…