Explaining principle trade-offs

Strong answers connect a principle to the change it prevents, the cost it adds, and signals that would reverse the decision. Example: DIP adds mapping layers but enables swapping Postgres for a fake in tests; you'd skip it for a throwaway script.

Interviewers want judgment, not slogans—name context, team size, and lifecycle.

On interviews: answer "Why SRP here?" with one reason to change protected and one cost of splitting.

Common pitfalls: citing acronyms without scenario, treating principles as absolutes, and ignoring delivery deadlines.

The trade-off is articulate design reasoning versus checkbox name-dropping.

Checklist:

• State protected change and added cost.
• Give a concrete codebase example.
• Name what would change your mind.