We significantly sped up our privacy proxy service by fixing a 40ms delay in "double-spend" checks. The issue stemmed from how Nagle's algorithm and delayed ACKs interacted with a third-party dependency.

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Cloudflare reduced double-spend check latency in their privacy proxy service from 40ms to under 1ms by fixing a TCP networking issue. The problem was caused by Nagle's algorithm and delayed ACKs interacting poorly when sending memcached commands in multiple small packets. The solution involved using BufWriter to buffer writes and send complete commands in single packets, eliminating the 40ms delay caused by TCP's delayed acknowledgment mechanism.

Reducing double spend latency from 40 ms to < 1 ms on privacy proxy

Theory 3: delays in Nagle’s algorithm and delayed acks