Day 8: Introducing SLA, SLO, and SLI for Engineering Leaders
Be Better Engineering Leader, a 30 Days Series
This is the second week of a series of daily lessons on how to Be a Better Engineering Leader. I recommend spending up to an hour on each lesson to gain insights into Product, Technology, and People—areas critical for every Engineering Manager.
Reliability is not just a technical requirement; it's a critical feature of your product. Even with fast and frequent releases, your product loses value if it's unreliable.
By defining and monitoring Service Level Indicators (SLIs), Service Level Objectives (SLOs), and Service Level Agreements (SLAs), you can maintain a balanced focus on innovation and stability.
Key Concepts
Reliability: The ability of your service to perform its intended function under stated conditions over a specified period. It ensures your application meets customer expectations consistently.
The "Nines" of Reliability: A shorthand for describing system uptime, expressed in percentages like 99.9% (three nines) or 99.999% (five nines). For example, 99.9% uptime allows for 43 minutes of downtime per month, while 99.999% permits only about 26 seconds. It was already proved that each additional "nine" represents an exponential increase in effort and cost for diminishing returns.
Error Budget: The acceptable level of unreliability, calculated as the complement of your SLO. It allows you to balance innovation and reliability by deciding when to invest in reliability work and when to focus on new features. For example, if your SLO is 99.9% uptime, your error budget is 0.1% downtime.
SLI (Service Level Indicator): A metric that measures the reliability of your service, like uptime, latency, or error rate.
SLO (Service Level Objective): The target you set for your SLIs, such as 99.9% availability.
SLA (Service Level Agreement): The formal commitment to customers regarding the minimum acceptable level of service, with penalties for failing to meet it.
Action Points: Define Your First SLIs and SLOs
Identify Key SLIs
Choose What to Measure: Focus on metrics that directly impact user experience. Common SLIs include availability, latency, or error rates.
Leverage Existing Tools: Use tools like Firebase Crashlytics for mobile app stability, Sentry or Bugsnag for web apps, and cloud observability tools for backend services.
Establish SLO Targets
Define Realistic SLOs: For each SLI, set achievable targets based on current performance. For example, aim for 99.9% crash-free sessions or 99.99% API uptime.
Engage Stakeholders: Share these targets with your team and business stakeholders to align on expectations and priorities.
Set Up Monitoring and Alerting
Choose Your Approach: Decide whether to monitor metrics manually or set up automated alerts. Tools like Grafana, Prometheus, or New Relic can help automate this process.
Define Alert Thresholds: Establish thresholds that trigger alerts when metrics approach the SLO boundary. This helps you address issues proactively.
Implement and Track Progress
Create a Shared Dashboard: Visualize your SLIs and SLOs using a dashboard tool like Grafana. This keeps everyone on the same page and allows for quick status checks.
Regular Review: Schedule regular reviews (weekly or bi-weekly) to evaluate performance against SLOs and adjust targets as needed.
Set an Error Budget
Define Acceptable Failure Levels: An error budget specifies how much unreliability is acceptable. For example, if your SLO is 99.9% uptime, your error budget allows for 0.1% downtime.
Adjust Priorities Accordingly: If you're under budget, you can focus on feature development. If you're over budget, prioritize reliability work.
Extra Resources
Premium Article with Templates: Leverage this introductory article that includes FigJam and Notion templates to help define and track your SLIs and SLOs.
Google's Comprehensive Guide: For deeper insights, read The Art of SLOs from Google's SRE team.
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