Weekly Tech Notes #19: Availability

🎬 A video about the difference between SLIs, SLOs and SLAs. In a nutshell, SLIs drive SLOs, which in turn inform SLAs. More specifically:

  • SLIs are Service Level Indicators or metrics over time which inform about the health of a service (e.g. 95th percentile of latency over last 5 minutes)
  • SLOs are Service Level Objectives agreed upon bounds for how often those SLIs must be met (e.g. 95th percentile SLI will succeed 99,9% over the year)
  • SLAs are business-level agreements which define the service availability for a customer and the penalties for breaking that availability

📚 Availability is an important concept for distributed systems. There’s math behind it, but also reasonable rules of thumb to follow. This week, I’m sharing a few articles that cover the topic.