Egress is the cost of sending bytes out to viewers — data transfer out of the CDN (and out of the cloud). For most OTT platforms it is the single largest recurring expense, because it scales directly with the thing the business wants to grow: hours watched at a given bitrate by a given number of concurrent viewers.
Egress cost is roughly bitrate × watch time × audience, which is why almost every cost lever in streaming touches it: a higher cache-hit ratio shifts bytes from expensive origin egress to cheaper edge egress; per-title encoding lowers the bitrate term; codec upgrades (HEVC, AV1) cut bytes for the same quality; multi-CDN and committed-volume contracts cut the unit price. CDN pricing itself is often tiered or billed at the 95th percentile of throughput, so smoothing peaks matters too.
Because egress dominates the P&L, modeling it accurately — per region, per CDN, per device class — is fundamental to OTT cost engineering and to deciding whether a given content or quality strategy is sustainable.
