Vocabulary · Volume 1 and Volume 2
Headroom
The deliberately unused portion of capacity, bought on purpose to absorb demand and failure. Calculate it as usable capacity minus demand under the same stated conditions, and say which state you mean: in Chapter 2, 16,000 minus 10,000 leaves 6,000 requests per second normally, but 12,000 minus 10,000 leaves only 2,000 after one failure group is lost.
Discussed in the book
Chapters where “Headroom” is discussed at length, ranked by how directly each section treats it.
- Volume I, Chapter 2: Capacity Is a Decision
Sections: How to read this chapter
- Volume I, Chapter 9: Orchestration and Agentic Topologies
- Volume II, Chapter 15: The Long Tail and the Spike
Sections: Put an investigation threshold next to the headroom · How to read this chapter · A small change can spend the remaining headroom
- Volume II, Chapter 19: Managing Risks and Anomalies