SLO Target Too Tight vs Too Loose: Finding the Right Number

The wrong SLO target is worse than no SLO. The right number is the one teams actually defend.

Two failure modes

The wrong SLO target is worse than no SLO. Two distinct failure modes destroy trust in the metric: too-tight targets get ignored, too-loose targets become decoration. Both signal the SLO does not match reality.

• Too tight. Target routinely missed; team learns to ignore burn-rate alerts; the SLO becomes noise then disappears.
• Too loose. Target never threatens to miss; the metric is decoration; product and engineering both stop checking it.
• The shared symptom. Nobody reads the SLO dashboard; nobody defends the budget; the discipline collapses.
• The right number. The one teams actually defend in planning meetings; achievable with effort, missed under stress.

Four-step landing process

• 1. Measure baseline for 30 days; no target.
• 2. Identify failure modes in that period.
• 3. Set target above achieved baseline (engineering ambition).
• 4. Validate with stakeholders.

Negotiating with product

Product and engineering want different things from an SLO. Product wants "always works"; engineering wants "achievable." The negotiation produces the number that survives both perspectives.

• Product asks for 4 nines. Engineering capacity allows 3 with current investment; the gap is the negotiation surface.
• Frame it as a budget. 4 nines costs 10x more than 3; the question is whether the user-visible benefit justifies the investment.
• Engineering asks for "achievable." The number engineering will actually defend; below that, the SLO becomes decoration.
• Document the decision. Both sides sign off on the number; the joint authorship survives personnel turnover.

Adjusting honestly

SLOs need adjustment when the user-perceived experience changes; they need protection against gaming via post-miss adjustment. The cadence (annual revisit, quarterly check) anchors the discipline.

• When to adjust. User-visible experience changed; product launch raised the bar; competitor parity demands tightening.
• When not to adjust. After a miss; that’s gaming; the data exists for a reason and the miss is part of it.
• Annual revisit. Scheduled review of every SLO; even if no change, the conversation revalidates the number.
• Quarterly check. Lighter-touch sanity check; achievement vs target, trend, recommended action; catches drift early.

Antipatterns

• Aspirational SLO never reached. Erodes trust in the discipline.
• SLO matched to current performance. No engineering ambition.
• Adjusting after every miss. Cooks the books.

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.