✏️ Explanatory Question
Bandwidth is QPS multiplied by payload size, calculated separately in each direction.
Ingress (incoming) = write QPS x average request size
Egress (outgoing) = read QPS x average response size
Worked example: a photo service at 3,000 read QPS serving 100 KB images.
That figure immediately tells you a CDN is required, since serving 2.4 Gbps from origin servers is both slow for distant users and expensive.
Remember to convert carefully: bandwidth is normally quoted in bits per second, but payload sizes are in bytes, so multiply by 8.