Creating meaningful Service Level Objectives (SLOs) is one of the most important steps in Site Reliability Engineering (SRE). When combined with Service Level Indicators (SLIs) and visual dashboards, you gain visibility into your system’s health and make better decisions about releases, incident response, and engineering focus.

This beginner-friendly guide offers a step-by-step walkthrough to help you get started.

Understand the Building Blocks

What is an SLI?

A Service Level Indicator (SLI) is a measurable metric that reflects the quality of service.

Think: What would a user notice if this broke?

Examples:

• Availability: % of successful HTTP 200 responses

• Latency: % of requests served in under 300ms

• Error rate: % of failed login attempts

What is an SLO?

A Service Level Objective (SLO) sets a target for the SLI.

Example: - 99.9% of requests should return HTTP 200 - 99% of search results should load in < 500ms.

What is an Error Budget?

The inverse of your SLO - how much downtime is allowed. - If your SLO is 99.9%, your error budget = 0.1% of requests can fail (43.2 mins/month).

Identify What Really Matters

Your SLO should reflect user impact. Use logs, customer feedback, or analytics to decide what matters most.

Example: E-Commerce Checkout API

• SLI: % of checkout requests returning 2xx within 400ms

• SLO: 99.5% over a 30-day window

• Error Budget: 0.5% or ~3.6 hours/month of allowed slow/failure cases

Track SLIs With Real Metrics

To track SLIs, use your existing monitoring stack (e.g., Prometheus, Datadog, or your platform’s native dashboarding tool)

Prometheus Example:

record: slo:checkout_success_rate
expr: sum(rate(http_requests_total{status="200", job="checkout"}[5m])) \
/ sum(rate(http_requests_total{job="checkout"}[5m]))

This expression calculates the success rate of your checkout service in 5-minute windows.

Build a Simple SLO Dashboard

Use Grafana, Datadog, or your platform’s native dashboarding tool to visualize: - SLI over time - SLO compliance (target vs. actual) - Remaining error budget - Burn rate (how fast you're consuming the budget)

Burn Rate Panel Example:

If your SLO is 99.5% and 1% of requests are failing now, your burn rate = 2x. That means you’ll exceed the budget twice as fast.

Set Up Alerts

• Set up alerts for

• Short-term burn rate: High failures in the last 5 mins

• Long-term trend: Steady degradation over 1–2 days

This helps balance between rapid response and long-term reliability trends.

Review and Adjust

Don’t set your SLOs in stone. Review them monthly: - Are they too tight? (Frequent false alerts?) - Too loose? (Incidents happening without alerting?) - Still aligned with user experience?

hint:Collaborate with product teams to update based on changing user expectations.

Final Thought

1. Choose SLIs based on user experience

2. Define realistic SLOs with your team

3. Track metrics with monitoring tools

4. Visualize performance on a dashboard

5. Set alerts based on burn rate

6. Iterate with regular reviews

SLOs aren’t just numbers—they’re how your users experience your system. Done right, they help prioritize engineering work, reduce burnout, and build reliable systems users love.

Follow me on Hashnode naveen yedla for more practical guides on SRE and cloud engineering!