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

Too tight: routinely missed; team learns to ignore.

Too loose: never threatens to miss; the metric is decoration.

Both signal the SLO does not match reality.

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 wants 4 nines; engineering capacity allows 3.

Product wants the SLO to mean ‘always works’; engineering wants it to mean ‘achievable.’

Negotiate honestly; document the decision.

Adjusting honestly

Adjust SLOs when the user-perceived experience changes. Avoid adjusting because of recent misses (that’s gaming).

Annual revisit; quarterly check.

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.