Latency Is Cheap, Bandwidth Is Not

The first time I really understood this, I was staring at a billing dashboard at 11 p.m., trying to explain to a VP why our AWS bill had doubled in a single month. We hadn't added significant compute. We hadn't provisioned new databases. What we'd done, quietly, as part of a feature nobody thought twice about, was start returning full user objects from a search endpoint instead of IDs. Forty fields per record. Hundreds of records per page. Millions of requests per day. The math, once you actually run it, is brutal. AWS charges roughly $0.09 per GB for the first 10 TB of outbound egress. That sounds trivial until you realize that 500 TB of monthly egress — a number that a moderately successful video platform reaches without trying — lands you somewhere around $37,500 every month. For moving bytes. Not for compute, not for storage, not for the engineering talent that built the thing. Just for the physical act of electrons crossing a boundary Bezos drew on a map.