Amazon Web Services

By the early 2000s, Amazon's engineers were burning weeks of effort spinning up compute, storage, and databases for every new project. So they built a standardized set of internal infrastructure services with clean APIs to make themselves faster. In 2006, Amazon flipped that internal plumbing into public products, S3 and EC2, and let any developer rent computing power by the hour. Within a few years a side effort was quietly outearning the retail business that spawned it.

This is the rare case where a company's cost center became its profit engine, and the question it forces is uncomfortable: how do you tell the difference between a tool you built to survive and a product the whole market would pay for? Founders and operators sitting on hard-won internal capabilities will recognize the tension. The case sharpens the instinct for spotting an asset hiding in plain sight, without handing you the rule for when to sell it.