Comparison
Brooks's lawvsCognitive load
Brooks's law
three engineers joined the late project and the next month was slower than the one before.
Adding people to a late software project makes it later. The mechanism is onboarding and communication overhead: new people consume the time of the people who know things, and the number of communication paths grows faster than the headcount. It does not mean never add people — it means the payback period is measured in months, so growing a team is a solution to next quarter and never to this deadline.
Full entry →Cognitive load
the team owns nine services and can explain four of them.
The total amount a team must hold in its head to do its work — domains, systems, tools, on-call surface. Treating it as a budget is the most useful team-sizing idea of the last decade, because it explains why adding one more service to a team can halve its throughput. It is also the strongest argument available against a proposed split or acquisition of ownership: not that the work is too much, but that the understanding required is.
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