How do you set an SLO target, and why not just aim for 100%? [Basic]
Answer
I set an SLO based on user expectations, business impact, dependency limits, historical performance, and the cost of reliability. I do not aim for 100 percent because perfect reliability is usually impossible, extremely expensive, and slows safe change.
Technical explanation
A good SLO is tighter than current customer pain but realistic enough to allow releases, maintenance, and controlled failure.
100 percent creates a zero error budget, meaning any failure would block change even when users are not materially impacted.
SLOs should be revisited as architecture, traffic, and customer expectations change.
Hands-on example
Example: historical checkout availability is 99.94 percent. Set an initial SLO of 99.9 percent over 28 days, leaving about 43 minutes of error budget per month. If the team burns less than 25 percent of budget for several quarters, consider raising the target.
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