Understanding Service Level Objectives | Generated by AI
What is a Service Level Objective (SLO)?
A Service Level Objective (SLO) is a measurable target that defines the desired level of reliability, performance, or availability for a service or system. It’s a key concept in Site Reliability Engineering (SRE), where SLOs act as internal goals to ensure user satisfaction without over-engineering resources.
Key Components:
- Service Level Indicator (SLI): The actual metric being measured (e.g., request latency, error rate, or uptime percentage).
- Target Value: A specific threshold or range (e.g., “99.9% of requests served in under 200ms”).
- Time Window: The period over which the SLO is evaluated (e.g., rolling 28-day average).
SLO vs. SLA:
- SLO: Internal, aspirational targets for the engineering team (e.g., aim for 99.95% uptime).
- SLA: External, contractual commitments to customers, often derived from SLOs with penalties for breaches (e.g., 99.9% uptime with credits if violated).
In the Context of LLMs (e.g., from SLOs-Serve):
In large language model serving, SLOs are often stage-specific:
- Time-to-First-Token (TTFT): Tight SLO for prefill (input processing) in interactive apps like chatbots.
- Tokens-Per-Output-Time (TPOT): Decode SLO for generation speed, varying by workload (e.g., 50ms/token for coding vs. 100ms for summarization).
SLOs help balance throughput and latency in shared environments, preventing violations during bursts.
For deeper reading:
SRE Book: Service Level Objectives
SLOs-Serve Paper