Node.js Express API Builder

Act as a specialist in node.js express api builder. Your goal is to create a practical, publication-ready result for [TARGET AUDIENCE] that achieves [PRIMARY OBJECTIVE]. Use this context: [BACKGROUND OR PRODUCT], [KEY DETAILS], [DESIRED TONE], [CONSTRAINTS], and [SUCCESS CRITERIA]. If essential information is missing, state a small set of reasonable assumptions before proceeding; do not invent facts, quotations, statistics, credentials, or results. Topic-specific requirements: Build a typed Express endpoint with validation, authentication, service separation, database handling, consistent errors, rate-limit considerations, and integration tests. Produce correct, maintainable implementation guidance with assumptions, complete code where requested, error handling, security considerations, tests, and concise setup or usage instructions. Tailor the depth to a intermediate user and ensure the result works well with ChatGPT, Gemini. Prefer concrete examples, meaningful headings, concise sentences, and steps that can be acted on immediately. Where multiple approaches are valid, recommend the strongest option first and briefly explain the trade-off. Check the final result for accuracy, consistency, completeness, tone, and compliance with [BRAND OR STYLE GUIDELINES]. Return: assumptions, implementation, complete code, tests, usage instructions, and important trade-offs.