harsh817 Design It Twice
Definition
Explore multiple designs before committing. Ousterhout's design-it-twice principle reduces tactical choices by forcing comparison of tradeoffs, complexity, information hiding, and future change cost.
Questions To Ask
- What are two or more reasonable ways to design this feature?
- Which design has the simpler interface?
- Which design hides more complexity behind the right module?
- Which design creates fewer dependencies and fewer special cases?
- Which design is easiest to test and evolve?
Existing Project Comparison
- Compare each option with current architecture, ownership, naming, data access, and test patterns.
- Reject options that require broad unrelated changes.
- Flag any option that only seems easy because it pushes complexity onto callers.
Suggestive Plan
- Sketch Design A.
- Sketch Design B.
- Compare complexity, dependencies, interfaces, data impact, tests, and failure handling.
- Choose a design with rationale.
- Record rejected alternatives in the feature design document.
Example
Option A exposes separate validate, save, and notify calls. Option B exposes updateRequestWindow and hides validation, persistence, and notification. Prefer B if it keeps callers simpler.
Vocabulary
- Design alternative: a plausible implementation approach.
- Tradeoff: benefit and cost of one design choice.
- Deep design: simple public surface with useful hidden behavior.
- Tactical choice: quickest local option that may increase future complexity.
Expected Outcome
Produce at least two design options, a comparison table, selected design, and rationale.