Throughput on the wire
Bandwidth estimation measures the data rate, in bytes or bits per second, that crosses a link. It is QPS multiplied by the size of each response or request.
Building it up
- Take the request rate, your QPS.
- Multiply by the average payload size in bytes.
- That gives bytes per second, which you can convert to bits by multiplying by eight.
If 1000 QPS each return a 50 kilobyte image, that is 50 megabytes per second outbound, or about 400 megabits per second.
Split the directions
- Ingress is data coming in, like uploads.
- Egress is data going out, like serving media, and is often billed more.
Egress to the public internet is usually the expensive direction, so media heavy systems lean hard on caching and content delivery networks to cut it.
Key idea
Bandwidth is QPS times payload size, split into ingress and egress, with egress usually the costlier and tighter constraint.