Methodology

Overview The core philosophy of SRE is: manage reliability through engineering methods. The most important tools are SLI, SLO, and Error Budgets. SLI: Service Level Indicator SLI is a quantitative metric for system reliability. Common SLIs include: Availability: successful requests / total requests Latency: P99 response time < 200ms Throughput: QPS > 10000 Correctness: data consistency check pass rate Key principle for choosing SLIs: start from the user’s perspective. Users don’t care about your CPU usage — they care whether requests succeed and are fast enough....

Overview Many teams treat SRE as just “operations with a new name” — hire a few people who can write scripts, change their titles, and call it a transformation. This mindset ignores a fundamental truth: SRE is an engineering methodology, not a toolchain. When Google created the SRE function in 2003, the core idea was “treat operations problems with software engineering methods,” which fundamentally changed the positioning, workflow, and culture of operations....

Overview Performance issues are among the most common scenarios every SRE encounters: users report “it’s slow,” alerts say “P99 latency exceeds threshold,” monitoring shows “CPU is almost maxed.” But many teams handle performance issues with a “tune wherever it’s high” approach — add machines when CPU is high, add indexes when SQL is slow, add cache when latency is high. This symptomatic treatment may work short-term, but over time it makes the system increasingly complex, costs keep rising, and problems become harder to troubleshoot....

Overview The first dilemma many teams face when practicing SRE is: they know what an SLO is, but they don’t know how to set one. They either copy Google’s 99.99% or pick an arbitrary 99.9% — only to find that the number neither reflects user experience nor drives engineering decisions. A good SLO isn’t plucked from thin air. It’s derived from business goals through a series of engineering methods: user journey analysis, metric selection, value calibration, multi-tier design, and regular review....