Service Level Indicator
A Service Level Indicator (SLI) is a quantitative measure of a specific aspect of a service's performance, such as availability, latency, or throughput, used to assess how well the service meets user expectations. It is a core component of Service Level Objectives (SLOs) and Service Level Agreements (SLAs), providing objective data to track service reliability and quality. SLIs are typically expressed as metrics like error rates, response times, or uptime percentages, derived from monitoring systems.
Developers should learn and use SLIs to establish clear, measurable targets for service reliability, enabling data-driven decisions about performance improvements and resource allocation. This is critical in DevOps and SRE (Site Reliability Engineering) contexts for maintaining high-quality services, prioritizing bug fixes, and balancing feature development with stability. Specific use cases include setting availability goals for cloud applications, defining latency thresholds for APIs, or monitoring throughput in microservices architectures.