Mon, 01 Jan 0001 00:00:00 +0000

The Tail of Two Metrics

When a colleague casually remarked, “Let’s use average response time to show how much faster the query API got,” I felt a sudden spike in my own latency.

I managed to contain myself, though my voice still came out cold. “Why use the average? Just because it makes our optimization look good?”

He stared at me blankly. “Why shouldn’t I?”

“Because P99 degraded!” I said. “Do you even know what P99 measures?”

About

Mon, 01 Jan 0001 00:00:00 +0000

I’m Xingyu Zan, a software engineer and builder.

I’ve spent much of my career working on backend systems: distributed systems, payments and accounting, migrations, reliability, and the operational problems that appear when software meets production.

This site is where I keep the work I want to own: essays, projects, experiments, and things I’ve learned by building them.

Elsewhere on the internet, I usually go by shinyoo.