A 99.9% monthly availability SLO allows roughly how much downtime per 30-day month?
Options
- ~4.3 minutes
- ~43 minutes (Correct option)
- ~7.2 hours
- ~1 day
Answer
~43 minutes
Why
30 days = 43,200 minutes. 0.1% of that is about 43 minutes of allowed downtime per month.
Each extra 9 divides it by 10: 99.99% ≈ 4.3 minutes per month.
Vocabulary: SLI = what you measure (e.g. % successful requests); SLO = your internal target; SLA = a contract promise to customers, with penalties.
Remember
99.9% ≈ 43 min/month; 99.99% ≈ 4 min/month.