What practice improves long-term maintainability when using modular designs?

• A. Rely on undocumented, ad-hoc connections between modules.
• B. Document interfaces and maintain modular components.
• C. Avoid updating modules after deployment.
• D. Establish maintenance procedures and use interchangeable parts.

Answer: (D)

Long-term maintainability in modular designs comes from establishing maintenance procedures and using interchangeable parts. When you have a clear process for updating, testing, deploying, and rolling back changes, the system stays reliable even as modules evolve. Interchangeable parts, built with standardized interfaces, allow swapping in upgrades or replacing a faulty module without rewiring the whole system, reducing risky, wide-ranging changes. This combination keeps the design adaptable and easier to maintain over time. Relying on undocumented connections creates hidden, fragile dependencies; documenting interfaces is helpful but incomplete without a maintenance process and interchangeable components; and avoiding updates blocks improvements and long-term upkeep.