I have recently read this article about a good ratio between developers and software quality assurance people and I am wondering if there is a similar concept for developer / non-developers in a SCRUM team.
This is caused due to the fact that current and previous work contexts for me is very different:
old context - SCRUM team of 5-6 developers, one tester (test cases, some manual testing), one tech-lead (highly technical, most of the time spent writing code, significant fraction during mostly technical meetings), the PO, one people manager that manages three SCRUM teams in total, a fraction of a SCRUM master. People manager is typical "formerly technical", but writes no code in this role
current context - SCRUM team of 2-3 developers, 1/2 tester (i.e. also involved in another project), one "team leader" that should handle people manager tasks and spend a significant fraction tackling stories (i.e. writing code), the PO. The team leader is typically involved in so many meetings (both technical and non-technical) that they spend less than 10% of their time writing code
After working more than one year in each setup, I feel that the first context that has a lower ratio of non-developers to developers is significantly more efficient.
Another source of inefficiency for the second text might be related to having the same person work in both "interrupted mode" (meetings, discussions, etc.) and "focused-mode" (continuous-time allocated to a single activity such as coding), but that's outside of current question focus.
Are there any recommendations related to the ratio between developers and non-developers in a SCRUM team?