SLO-Driven Incident Postmortems

Postmortems with no SLO context are stories. With SLO context, they are accounting.

The pre-SLO postmortem trap

Postmortems without SLO context become stories. With SLO context, they become accounting; each minute of impact has a measurable cost.

• Without SLO context. Postmortems list events, assign 'learnings', rarely change behaviour.
• With SLO context. Each minute of impact has a measurable cost in budget; trade-off conversations sharpen.
• Behaviour change. Quantifying impact converts vague follow-ups into specific budget-protecting investments.
• Across-incidents view. Cumulative budget impact across the quarter shows whether postmortems are reducing harm.

Four-section template

• 1. SLO impact: minutes consumed; budget remaining.
• 2. Timeline: events; decisions.
• 3. Root cause: what failed; why.
• 4. Action items: dated; owned.

Budget attribution math

The math is straightforward; the discipline is doing it consistently. Each postmortem tags its budget impact and the cumulative trend tells the real story.

• Per-incident calc. Incident impact duration divided by window budget equals percent of budget consumed.
• Tag in postmortem. Number lives in the postmortem template; visible alongside the timeline and root cause.
• Quarterly cumulative. Sum across the quarter; trend tells you whether reliability is improving or eroding.
• Per-team view. Per-service, per-team budget impact; surfaces which teams need more reliability investment.

Action items that ship

The point of an SLO-driven postmortem is action items that ship. Each one references the budget it would protect; checklists without that link are theatre.

• Budget-protecting. Each action item references the budget impact it would prevent in a future similar incident.
• Owner and date. Named owner, target date; tracked alongside feature work in sprint planning.
• Sprint visible. Action items appear on the sprint board; the team commits to them, not aspires to them.
• Closure tracked. Quarterly review of completed action items; uncompleted ones surface in the next retro.

Antipatterns

• Postmortem with no budget impact. Disconnected from the SLO program.
• Action items with no owner or date. Wishes.
• Action items not tracked in sprint planning. Forgotten.

What to do this week

Three moves. (1) Apply the pattern to your most-impactful service. (2) Measure adherence for 30 days. (3) Rewrite the policy or the SLO if the gap is durable.