98.64 % uptime? It felt like I was blocked 44 % of the time.

Martin Rau · · 3 Min. Lesezeit

There’s a SaaS metric that shows up in every status report, every marketing slide, every SLA table: uptime. The vendor in question proudly puts 98.64 % on the wall. Sounds like a system that’s basically always running. Sounds like one day of downtime in two and a half months. Sounds like: everything under control.

My gut said otherwise. So I counted.

The stripes

The vendor visualises status as bars over time — one stripe per day, coloured by state. Green means: all good. Red and orange mean: something happened.

I ran the image through a pixel classifier and counted the bars. The result for claude.ai over 90 days:

  • Green: 50 bars → 55.6 %
  • Red: 32 bars → 35.6 %
  • Orange: 8 bars → 8.9 %

Put differently: on 40 out of 90 days, the stripe wasn’t green. That’s 44.4 %.

Where the gap between 98.64 % and 55.6 % comes from

Both numbers can be true at the same time — and that’s exactly the problem.

Uptime is usually measured as a ratio of “service technically reachable” to “total elapsed time”. If a component tips over for 20 minutes, you lose a couple of hundredths of a percent. The day stays mathematically almost entirely green. On the status board, though, it gets flagged as an incident — so the stripe isn’t green.

That creates a skewed logic:

  • Vendor view: “We were only down for 20 minutes, that’s 0.02 % of the month.”
  • User view: “On that day my build failed, my deploy slipped, my meeting got pushed. The day wasn’t fine.”

The 98.64 % measures seconds. My gut measures workdays. And workdays aren’t a linear unit — a 15-minute outage at the wrong moment costs half a day of flow, not 15 minutes.

What the more honest number would be

If you measure uptime the way it actually affects usability, the statement here isn’t “98.64 % uptime”, it’s:

What I take away from it

  • Uptime percentages are a PR format, not a user format. Technically correct, simultaneously misleading if you read them 1:1 as reliability.
  • Status boards with daily stripes are more honest than SLA numbers — because they show exactly what you feel as a user: was the day disrupted or not?
  • When the gut diverges from the metric, the gut usually isn’t wrong. It’s just measuring something other than what the vendor measures — and often the more relevant thing.

Maybe alongside “uptime” a second number should become standard: incident-day rate. Share of days with at least one reported incident. Here that’s 44 %. And suddenly that matches reality quite well.

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