You need to practice minimal design to be effective with systematic reuse. The design needs to continuously look for opportunities to align iteration goals with your systematic reuse roadmap. Too many developers mistakenly think that adopting agile means abandoning design. This couldn’t be farther from the truth.
You design whether you explicitly allocate time for it or not. Your code will reflect the design and you will impact the technical debt for your codebase in one way, shape, or form. Implementing user stories and paying down technical debt should be your end goal and not avoiding design altogether.
Always design for meeting your iteration goals. Avoid designing for several weeks or months and surely avoid putting technical elegance ahead of delivering real user needs. You should design minimally. Just enough to take advantage of existing reusable components, identify new ones, and plan refactoring to existing code. Specifically this means:
1. Keeping a list of short term and medium term business goals in mind when designing.
2. Always looking for ways to make domain relevant software assets more reusable.
3. You are aware of what distribution channels your business is looking to grow.
4. Design reflects the domain as close as possible and that your reusable assets map to commonly occurring entities in your business domain.
5. Value is placed on identifying the product lines that your business wants to invest in and evolving your reusable assets to mirror product line needs.
6. Design isn’t a pursuit of perfection but an iterative exercise in alignment with your domain.
What you decide to encapsulate, abstract, and scale are all natural byproducts of this design approach. Rather than spend a lot of effort with a one-time design approach you need to do just enough design.