P95 Disaster Line: How to Fix Your Startup's Worst User Experience

Hey Reader,

In the last 7 days, what's the worst experience any user had in your product?

Not a Sentry alert. Not a bug you patched.
I mean the worst real thing a user actually experienced.
Do you know? (if not, then observability)

And if you're pre-launch.. What do you think it will be?

Was that a one-off... Or does that happen to 1 in 20 people?

Your product isn't judged by the best experience.
It's judged by the worst experience that happens often enough to matter.

You already think in P95 terms, you just don’t call it that.

When you say 95% of users complete onboarding are you ignoring the 5% who don’t. That 5%? Are they really edge cases?

P95 is your disaster line:

• The point where 5% of users fall below acceptable.
• Not theoretical. Not rare. Not worth ignoring.

If your P95 API response time is 5s:

• 95% get a response in 5s or less.
• 5% wait longer, maybe much longer.
• They think your product is broken and they quietly leave.

P95 thinking is baked into how founders talk about their products in every dashboard. Every investor update. Every #BuildInPublic post on LI.

P95 is your disaster line. Actually. You choose your disaster line. What level of user pain are we willing to tolerate and still call the product good enough?

That's a company decision. A strategic one. The minimum experience you're okay being judged by.

Move the P95 experience. Now only true edge cases have disaster. So 95% of users succeed on their first try.

That 1-in-20 disaster. It’s probably happening to someone right now. While you’re reading this.

If I can be of service, feel free to grab time.

LFG,
James