Sustain: Capacity, Cost, Energy and Lifecycle

Most of what an operator does about the future of a service is quiet: capacity is added before demand arrives, a certificate is renewed before it expires, a patch is applied inside its window, and a data centre reports its energy once a year. None of it produces an incident, and all of it decides whether the next incident is small. This chapter concerns O5 Sustain in its steady-state parts: capacity planning, the management of cost, the measurement and reporting of energy, and the lifecycle work that keeps an estate supportable. Chapter 12 takes the other half, the learning that follows incidents. Its actions are carried out through the change pipeline and checked against signals, so the chapter also touches O3 Change and O1 Observe.

AI enters this function through forecasting models embedded in capacity tools, through agents that propose or perform rightsizing, scheduling and clean-up, and through assistants that draft the lists of what is to be renewed, patched or retired. The most important design question concerns the second: an agent given the objective of lowering cost sees redundancy as waste. The chapter applies four conclusions of the earlier volumes. Patch decisions are delegated in advance, because a weekly advisory board cannot sit in the path of a known-exploited vulnerability (F29; AI Governance, Chapter 24) (296, Nordqvist, 2026). Small delegations erode the skill, capacity and fallback that the delegation replaced, so each delegation needs a reversibility test (F69; AI Threat, Chapter 26) (299, Nordqvist, 2026). A measure that becomes a target is gamed, and a machine can do so faster (F132; AI Purple, Chapter 18). And the autonomy budget of Chapter 4, with the Level 4 prohibitions it states, applies to every action class that this chapter mentions.

The five operations functions divide the work of keeping services running by the question each answers. O1 Observe asks what is happening, O2 Diagnose why, O3 Change what should be altered, O4 Restore how to return to a good state, and O5 Sustain how to remain fit over time. The last of these has a different clock from the others. An incident is measured in minutes and hours, a change in hours and days, and the work of this chapter in weeks, quarters and years: the lead time to procure hardware, the length of a certificate, the interval between an upstream release and the patch window, the filing date of an annual energy report.

Primary topics explored

1. What Sustain keeps steady
2. Capacity planning
3. Cost and FinOps
4. Agents that optimise
5. Energy and carbon
6. Lifecycle