What are service level objectives?
A Service level objective (SLO) is a target goal established using monitoring data. It measures service performance and helps identify patterns—such as reliability issues during code deployments or predictable availability trends. This information enables better service forecasting and operational planning.
A well-defined SLO helps determine the optimal reliability level for your service's customers. It establishes two critical thresholds: an upper bound where customer satisfaction is met, and a lower bound that signals when reliability investments are necessary.
SLOs are fundamental to business value delivery. They provide visibility into whether your products and services meet customer expectations and offer a pragmatic framework for managing reliability— acknowledging that 100% reliability is often neither achievable nor cost-effective.
One of the key strengths of SLOs is their flexibility. They can be broad or specific, depending on the metrics you choose, and because they are internal tools, they can evolve with your business needs.
Why SLOs?
SLOs establish target metrics for a system's consistency and performance over time. Their measurement relies on service level indicators (SLIs)—specific metrics extracted from your monitoring infrastructure. SLIs statistical analysis provides the background for evaluating progress toward established goals.
Failing to meet its SLO can result in:
- Performance degradation
- Service outages
- Negative customer impact
- Business revenue loss
However, striving for perfect reliability (100% uptime) leads to exponentially higher costs, often resulting in:
- Slower software release cycles
- Overbuilt infrastructure
- Resources diverted from feature development
The key is finding the right balance. Since not all service disruptions have equal impact, aligning SLOs with business KPIs helps prioritize efforts between:
- New feature development
- Technical debt reduction
- Infrastructure improvements
By balancing potential risks against acceptable downtime, SLOs help define reasonable uptime goals—the key point is they create what's known as an error budget, a calculated allowance for inevitable imperfections.
The Service Level Objective Development Lifecycle (SLODLC) community— an open-source initiative led by Nobl9—develops enterprise-wide methodology for defining software service reliability and performance goals.
The SLODLC community brings together professionals across the SRE ecosystem to address SLO adoption challenges through:
- A standardized, repeatable methodology for SLO adoption
- Comprehensive playbooks for consultants and service providers
- An agile framework that integrates with existing practices