When is it appropriate to create a new application instead of adding more modules to an existing application?

Creating a new application is most appropriate when the new functionality represents a distinct business domain or user group, has its own lifecycle, or needs to be scaled independently. This approach allows for better separation of concerns, making it easier to manage, maintain, and evolve each application independently.

When an application serves multiple business domains or user groups, it can lead to complexity in both development and maintenance if everything is crammed into a single application. By creating a new application, you can tailor the architecture, performance, and scalability specifically to the needs of that distinct domain without affecting other functionalities. Moreover, having a separate lifecycle for the new application means that updates, deployments, and changes can happen without impacting the existing application, which reduces risks and enhances operational efficiency.

This approach is especially beneficial when scaling is a consideration, as different applications can be allocated resources based on their specific needs and demands, leading to optimized performance across your portfolio.