SaaS
SLA
- Service Level Agreement
- Five 9s:
- meaning availability of 99.999% of the time per year
- equates to 5 mins of downtime per year
- often referred to as perfect uptime as it is close to 100%
- very costly to achieve
- it is generally used as a goal for critical systems
- generally needed in telecommunications, eCommerce, financial service
- Generally 3-4 9s are sufficient for most use cases
| SLA - 9s | Downtime |
|---|
| 99.999% (5) | 5 mins |
| 99.99% (4) | 52 mins |
| 99.9% (3) | 8 hours 46 mins |
| 99% (2) | 3.65 days |
SLI
- Service Level Indicator
- key metrics that measure system performance and affect user experience
- Examples:
SLO
- Service Level Objective
- availability targets of a service
- SLOs = (successful events/total events) * 100
- Example:
- (success 200 / total requests) * 100
- Grafana supports setting alerts on SLO