Cloudflare identified a significant opportunity to improve the speed of its privacy proxy product, which allows users to browse the web without revealing personal information. The improvement focused on reducing the latency of "double-spend" checks related to Privacy Pass tokens, which initially took around 40 ms to complete. Using a combination of tracing and metrics, Cloudflare discovered that the latency was primarily caused by the interaction between Nagle's algorithm and delayed acknowledgments (ACKs) in their network communication. The team found that their implementation sent multiple small messages for a single command, leading to delays. By employing BufWriter to consolidate these messages into a single user-space memory buffer, the latency was reduced to less than 1 ms. The investigative process involved a systematic, data-driven approach, emphasizing observability tools, testable hypotheses, and the identification of subtle interactions in the code, ultimately contributing to a faster and more efficient Internet experience for users.