To design software that handles future features and performance, focus on modularity and scalability. Break the system into independent, reusable components, so adding new features doesn’t disrupt existing functionality. Use design patterns to tackle common problems flexibly and prioritize clear, maintainable code. Plan for scalability by designing for growth in user load or data size. Build with testing in mind, so changes can be verified easily. Finally, stay open to feedback and evolving requirements—no design is perfect from day one, so adaptability is key.

Break down the whole software in small pieces. These pieces would be components where you should start thinking how to write those. Define the nature of every component, you might find flows where design patterns work perfectly to manage the information as you need. For backend perspective, implement an architecture such as microservices. Try to keep simple every service. For frontend, you could implement microfrontend architecture using React, Angular or any modern UI framework. Finally, be sure that you understand very well the business reasons, that might help you to design and define components

One effective step which worked in our domain for a new product development, in making a software robust in design and scaleable for new features is to start with as much of requirements as possible including identifying potential changes, features required and start modeling the software in the form of class and sequence diagrams i.e., UML. Dividing the whole software into modules in manageable and extendable numbers is one of the approaches worked for me in my latest project. Few things to identify are messaging methods, format and making it extendable for new features between the modules, so they are still decoupled yet be able to interact with each other and function as one wholistic software solution.