Can I vibe code Ideal Postcodes?

Build a lightweight address lookup backend proxy service and frontend autocomplete component in Node.js and vanilla JavaScript.

1. DATA AND API ARCHITECTURE:
- Create a Express.js microservice endpoint GET /api/v1/address/autocomplete?query=:query
- Create a GET /api/v1/address/format?id=:address_id endpoint to fetch full structured address data.
- Configure the proxy to forward requests to an external provider (e.g., Ideal Postcodes API or OpenStreetMap Nominatim), injecting API keys via environment variables.

2. CACHING & PERFORMANCE:
- Implement an in-memory Redis cache for autocomplete results and formatted addresses using MD5 hashes of query parameters.
- Set a 30-day TTL for successful lookup responses to reduce redundant upstream API costs.

3. FRONTEND UI WIDGET:
- Create a framework-agnostic, accessible JavaScript input field widget with debounced keystroke handling (300ms).
- Render an accessible dropdown menu showing up to 10 suggested matches.
- On selection, populate hidden form fields for address_line_1, address_line_2, city, postcode, and country_code.

4. FAILURE MODES & ERROR HANDLING:
- Handle upstream API rate limits gracefully with exponential backoff and fallback to manual address entry mode.
- If external search returns 0 results or throws an error, display an explicit 'Address not found — enter manually' toggle for the user.
- Sanitize all user input strings to prevent XSS and SQL/NoSQL injection vulnerabilities before processing or caching.

5. OUT OF SCOPE:
- Do not attempt to store raw PAF databases or self-host full UK geospatial data.
- Do not implement custom credit billing systems.

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