Are they still a pure AWS house? I'd expect that, at their scale, they'd have boxes and VMs everywhere the round-trip time justifies.
They use AWS for everything except content delivery which is handled by their Open Connect content delivery system that they built and operate. https://openconnect.netflix.com/en/
Interesting. For a moment I thought they would aggressively optimize encoding for frame cost but then I realized that's probably a rounding error compared to their costs in storage and co-located infrastructure.
They have boxes at every major ISP borders, but they're solely caching infrastructure.
They publicly advertise this under the "Netflix Open Connect" initiative: