(Opinions are my own) As someone who has worked for a long time at small startups (<30 people, <10eng) my "20%" projects (what other people are referring to "1

(Opinions are my own) As someone who has worked for a long time at small startups (<30 people, <10eng) my "20%" projects (what other people are referring to "120%" here) that I've done on my own time have, in some cases, saved the companies I've worked for more than thousands of eng-hours and have taken less then a weekend. Attacking a core business problem from a new angle that no one else sees and designing a revolutionary approach to solving it that saves everyone time, money, and reduces stress is very common. Some examples of this from my previous job: 1. https://github.com/CaperAi/branchpoke https://github.com/CaperAi/branchpoke 2. https://github.com/CaperAi/bazel_compose https://github.com/CaperAi/bazel_compose 3. https://github.com/CaperAi/pronto https://github.com/CaperAi/pronto These were the ones that were easy to pluck from my job's monorepo and generally applicable. As someone who is leaving a small startup for Google I can also add that it's one of the biggest compensation-y things in the offer. My manager seems supportive of 20%ing, the project I'm on is an offshoot of a 20% project, and the skip level I spoke to supported the idea of building tools. So... From a management perspective the startups I've worked for have lost a senior engineer to another company more supportive of personal projects. This is very expensive as 1 senior engineer could represent 10%-40% of your eng team capacity at a small company. So, even just as an employee retention mechanism 20% of a salary spent on retaining your core engineering team and, possibly, obtaining huge benefits to overall company productivity is a worthy trade.