Cognitive Load
The total amount a team must hold in its head to work effectively, and a real constraint on how many services or domains one team can own.
Three kinds, from the Team Topologies framing. Intrinsic — the skills the work fundamentally requires. Extraneous — the incidental burden of environments, deployment mechanics, tooling and undocumented processes. Germane — the domain knowledge that is the actual value.
The architectural use of the idea is as a sizing constraint on ownership. A team owning twelve services across three domains is over capacity regardless of headcount, and the observable symptoms are consistent: slow onboarding, changes only one person can make, and services that quietly stop being maintained.
Two levers. Reduce extraneous load with a platform and a paved road — that is what platform teams are actually for, and it is why "we built a platform and nobody's velocity improved" usually means the platform added load rather than removing it. And re-draw boundaries so a team owns one coherent domain rather than fragments of several.
It is the practical mechanism behind Conway's Law: teams shape systems partly because they cannot hold more than a certain amount of system in mind.