Service level management

A service level is a promise with a number attached. The number is the easy part; choosing what to measure is where these go wrong.

Measure what the customer feels

The characteristic failure is a service meeting every target while customers are angry. It happens when the measure is chosen for availability of data rather than relevance:

• Uptime that excludes degraded operation. Technically up and unusably slow is down.
• Response time instead of resolution time. An instant acknowledgment that resolves nothing measures the autoresponder.
• Averages instead of percentiles. A mean hides the tail, and the tail is who complains. Commit at p95 or p99, not the mean.
• Measurement from inside your own perimeter, which excludes the part of the path the customer actually traverses.

Set targets you would fund