Engineering leadership · Book notes
An Elegant Puzzle's team sizing when output stops tracking headcount
Will Larson's team sizing rules hold because coaching and the pager scale with people, even when agents decouple output from headcount.
One question I keep coming back to is.. how big should a team be, once you’ve decoupled output from headcount? A good place to start thinking about team sizing is this essay by Will Larson: Sizing engineering teams, which is also reprinted in the book An Elegant Puzzle (Stripe Press, 2019). The core rule of thumb in that essay is: a manager should manage 6-8 engineers, and a manager of managers should manage 4-6 managers.
There are two more rules from Larson that I think are relevant here: an on-call rotation should have about 8 engineers so that the frequency of getting paged is low enough that people don’t get burned out, and teams should have at least 4 people because otherwise they’ll behave more like a group of individuals than a team. (Larson on exceptions: “I have regretted it every single time.”)
These numbers make sense to me given the purpose of a manager’s span: a manager’s week is mostly spent with people, coaching each individual engineer and reviewing their work. Hiring and career conversations take their own hours. Underpinning all of this is the duty that if someone goes on vacation (or resigns), it shouldn’t bring down the service. None of this scales with lines of code shipped. It scales with headcount and the pager.
This book is often viewed as a playbook for big tech in the growth era. I think some of the hypergrowth-hiring parts haven’t aged well, but the thinking behind the sizing hasn’t. It’s about people all the way through.. you spend the same amount of time coaching people, and you need to cover for absences the same way.
This is why a recent number stood out to me. Fortune reported that Meta’s applied AI engineering group runs at about 50 engineers per manager.. about double the 25 to 1 that’s usually treated as the outer limit of span. I’d push back on this stretch: no one can coach or review 50 people. At that ratio, the manager processes people rather than manages them. Agents add to the review load for the manager, but the coaching load stays the same.
I keep coming back to the small team. If you have 4 people who can ship what 8 people did, those 4 people still need to rotate without burning out, and someone still needs time to review what the agents are doing. The pager and absences fall on fewer people. I’m still not settled on whether the smallest real team is now set by the on-call rotation instead of the workload.