How reverse proxies handle concurrent requests at scale (ATS, HAProxy, Envoy)

I wrote a deep dive on how modern reverse proxies handle thousands of concurrent requests.

The article walks through what actually happens inside a proxy when multiple requests arrive at the same time: connection handling, request queues, event loops vs thread pools, and how different implementations approach the problem.

It also compares design patterns used in systems like Apache Traffic Server, HAProxy, and Envoy, and explains why these architectural choices matter for latency, throughput, and failure behavior.

The goal was to help zoom in what happens between the client and backend when traffic spikes.

Would love feedback from folks running proxies at scale.