Delivering HTTP/2 upload speed improvements

What this post added

This post details the investigation and resolution of slow HTTP/2 upload speeds, particularly for users with high bandwidth. The core issue was identified as insufficient receiver flow control in the HTTP/2 layer, specifically the fixed-size request body buffer in NGINX. The solution involved implementing an autotuning mechanism for the HTTP/2 request body buffer size, dynamically adjusting it based on the network's Bandwidth-Delay Product (BDP) to match or exceed HTTP/1.1 performance and achieve up to 3x improvement in production tests.