I’ve had the range of experiences with this. I’ve seen 2 instances someone running his own side business while on my team… one of them had some noticeable perfo

I’ve had the range of experiences with this. I’ve seen 2 instances someone running his own side business while on my team… one of them had some noticeable performance deterioration and the other seemed to not show much change. They were both top 10% engineers and remained so. I imagine the day job wasn’t very challenging for them. I’ve seen executives do this successfully with a consulting gig on the side, sitting on boards, etc. The trick to both scenarios seems to being paid for your attention in one job and your experience in the other.