backend-development

name	Backend Development
description	Next.js 15 + Cloudflare Workers + @vspo-lab/api client. Result-type error handling, OpenAPI-generated client, feature-based architecture.

Trigger

• When creating or editing files related to API client usage, data fetching, or server-side logic
• When adding new API integrations or modifying data flow patterns
• When working with packages/api/, packages/errors/, packages/dayjs/, or packages/logging/

Execution Checklist

1. Use @vspo-lab/api (VSPOApi) for all external API calls
2. Handle all results with Result<T, AppError> — no try-catch
3. Add JSDoc with preconditions and postconditions to public functions
4. Define types with Zod Schema First (z.infer<typeof schema>)
5. Use @vspo-lab/dayjs for all date/time operations — no raw Date

Reference Documents

• docs/backend/server-architecture.md - Next.js 15 on Cloudflare Workers, VSPOApi client, Result type, mock system
• docs/backend/function-documentation.md - JSDoc conventions (preconditions, postconditions)
• docs/backend/pr-guidelines.md - PR guidelines (current state, problem, implementation)
• docs/backend/datetime-handling.md - UTC-first date handling with @vspo-lab/dayjs