The key factor – team communication
A key element of the difference between microservices and monolithic architecture is the difference in the communication structure that they support.
If the monolithic application has grown organically from a small project, as usually happens, the internal structure can become messy, and requires developers with experience in the system who can change and adapt it for any change. In bad cases, the code can become very chaotic and be more and more complicated to work with.
Increasing the size of the development team becomes complicated, as each engineer requires a lot of contextual information, and learning how to navigate the code is difficult. The older teammates who have been around can help to train new team members, but they'll act as bottlenecks, and mentoring is a slow process that has limits. Each new member of the team will require a significant amount of training time until they can be productive in fixing bugs and adding...