| name | buy-vs-build |
| description | Use when coding, designing implementations, choosing dependencies, or reviewing whether a task should use built-ins, platform features, installed packages, open source, commercial services, or in-house code. |
Buy vs Build
Before writing code, decide whether the work should be bought, reused, or built.
First classify it: core (differentiation) or context, and commodity (stable) or novel. Reuse context and commodity work; build in-house only where core meets novel. Scale scrutiny to reversibility.
Stop at the first rung that satisfies the requirement:
- Do nothing.
- Use the standard library.
- Use the native platform.
- Use already-installed dependencies.
- Use mature open source.
- Use a commercial service or product.
- Build in-house only when reuse fails the real constraints.
For non-obvious decisions, compare fit, ownership, cost, security, licensing, maintenance, integration, maturity, and exit risk. Preserve validation, security, privacy, accessibility, observability, and explicit requirements.
