I have seen the startup stages of software projects with varying levels of quality. The whole spectrum from very bad to very good can be observed and/or partici

I have seen the startup stages of software projects with varying levels of quality. The whole spectrum from very bad to very good can be observed and/or participated in in the wild. The good ones start out with one experienced developer. After two or three features have been added (within two weeks to a month) more developers, possibly less experienced ones can be added. Their number should grow somewhat slowly mainly to make sure that they are not getting in each others way too much. Practices that make this work are automated testing and code review. Occasionally, some pair programming can be practiced, especially when some refactoring is needed. I am talking about limited refactoring here, maybe taking two to three days. If the project can be split in a front end and a back end one may start out with two developers. In theory a system that consists of N services might start with N developers but if N starts out larger than 3 one is quite likely engaging in over engineering.