When to Use SLI: Timing, Triggers, and Measurement Cadence

When should teams define and use SLIs?

SLIs are useful throughout a service’s lifecycle: from design and launch, through daily operations, and during incident response and strategic reviews. The right timing and cadence depend on the type of service, its impact on customers, and how quickly conditions change. Below is a practical guide to when SLIs are most valuable and how often they should be measured.

1. During Service Design and Launch

The earliest and arguably most important time to define SLIs is during service design. Before launching a new warehouse process, digital feature, or shipping option, identify the user journeys that matter and determine the SLIs that will indicate success. Early SLI definition ensures that monitoring, data collection, and accountability are built into the system from day one.

2. Before Contracting or SLA Negotiations

Define SLIs ahead of vendor negotiations. If you plan to include performance commitments in an SLA, your chosen SLIs must be precise, measurable, and auditable. Defining them early avoids disputes and ensures both parties can agree on measurement methodology and remediation.

3. Daily Operations and Continuous Monitoring

For operationally critical services, SLIs should be measured continuously and surfaced in near-real-time dashboards. Warehouse and transport SLIs such as throughput, on-time shipments, and error rates are often monitored hourly or daily. Rapid measurement helps frontline teams detect issues and keep operations within acceptable bounds.

4. During Incidents and Outages

SLIs are essential during incidents because they provide objective evidence of impact and recovery progress. When an SLI dips below a threshold, it should trigger alerts and an incident process. During remediation, teams use SLIs to track whether fixes restore the desired level of service.

5. Post-incident Reviews and Root Cause Analysis

After an incident, analyze SLIs to understand what went wrong, how long the service was degraded, and whether corrective actions were effective. SLIs give a factual timeline for post-mortems and help prioritize systemic fixes to prevent recurrence.

6. Regular Reviews and Continuous Improvement

Set a cadence for reviewing SLIs: daily operational standups, weekly logistics reviews, and monthly or quarterly executive reports. Regular reviews allow teams to spot trends, validate improvements, and adjust SLOs as the business evolves.

7. During Seasonal Spikes or Major Changes

When preparing for peak seasons, promotions, or major migrations, increase the frequency of SLI monitoring. Holiday peaks, large product launches, or system migrations can stress services in new ways; heightened SLI visibility reduces the risk of surprises.

8. When Rolling out Process or Technology Changes

Introduce SLIs before making significant process changes (like new fulfillment flows) or deploying technology upgrades. Compare pre-change and post-change SLIs to validate improvements or identify regressions. Feature toggles and canary deployments combined with SLIs can limit the blast radius of unintended problems.

9. When Customer Expectations Shift

If customers demand faster delivery windows or higher accuracy, update SLIs and SLOs to reflect new expectations. Use surveys and customer feedback to validate whether your chosen SLIs align with perceived quality.

Choosing the right measurement cadence

• Real-time/near-real-time: For operational SLIs tied to immediate customer impact (e.g., system availability, order processing pipeline).
• Daily: For metrics where one-day snapshots reveal issues (e.g., pick error rates, daily throughput).
• Weekly: For trends that need smoothing and context (e.g., carrier performance by lane).
• Monthly/Quarterly: For strategic SLIs reviewed by leadership (e.g., long-term customer satisfaction proxies, overall on-time delivery trends).

Practical example: onboarding a new fulfillment center

When an organization opens a new fulfillment center, SLIs should be defined during setup (what constitutes on-time and accurate picking), measured in near-real-time during the first weeks, reviewed daily to tune processes, and then moved to a longer-term cadence (weekly and monthly) once operations stabilize. Any dip during ramp-up triggers targeted root cause analysis and faster corrective loops.

When NOT to rely solely on SLIs

SLIs are powerful but they’re not a replacement for qualitative signals. Use SLIs alongside customer feedback, exception reports, and frontline observations. If you wait for an SLI to trigger action for a slowly worsening problem, you may have missed early qualitative warnings.

Conclusion

SLIs should be defined early, monitored according to the service’s risk and impact, and revisited whenever the service or customer expectations change. With sensible timing and cadence, SLIs become a continuous compass for operations, helping teams act faster and make better decisions.