Service Level Indicators (SLIs) and Service Level Objectives (SLOs) play a crucial role in keeping businesses performing at their best. The right SLIs and SLOs help ensure high-quality service delivery and customer satisfaction, especially when combined with a robust observability strategy. 

In fact, the 2023 New Relic Observability Forecast found that observability improves service-level metrics so much that those who had deployed full-stack observability experienced fewer outages, a faster MTTD (mean time to detect) and MTTR (mean time to resolution), and lower outage costs.

While the outcomes are impressive, defining SLIs and SLOs can be daunting.

Below are my top ten tips on defining effective SLIs and SLOs. 

1. Set realistic SLO targets. Avoid setting unattainable targets and allow some tolerance for negative events. This will prevent frustration and provide room for growth.
2. Align cross-functional teams. Involve product, engineering, and operations in defining SLIs and SLOs. Cooperation ensures that each party understands their responsibilities and how their work contributes to overall success.
3. Correlate SLOs with user impact. Prioritise SLOs that measure performance and availability, as these directly influence user experience.
4. Focus on critical user journeys. SLIs should measure not only services but also the essential user flows on which your customers rely.
5. Balance SLO stringency, cost, and user benefit. Over-engineering SLOs can be costly and unnecessary. Strive for flexibility as usage and demand grow.
6. Use error budgets effectively. Balancing opposing interests, such as innovation and reliability, becomes easier when using error budgets. Shift focus when the budget is exhausted in order to maintain a balanced approach.
7. Track error budget trends. Measure the error budget's rate of change over short and long periods to provide enough headroom for pre-emptive action against potential violations.
8. Understand event-based and time-based SLIs. Comprehend the pros and cons of each method as they make different assumptions and measure varying outcomes.
9. Establish a plan for SLO violations. Encourage shared responsibility among teams by having an agreed-upon plan in place to handle any violations that may occur.

Reevaluate SLO targets as usage grows. As demand increases, adjust your SLO targets accordingly, ensuring that your organisation continues to meet the needs of your users.

By incorporating SLIs and SLOs into your observability strategy, your engineers – as well as your business – will be set up for success now and into the future.