| name | nextjs-data-access-layer |
| description | Build secure, reusable data access patterns with DTOs, taint checks, and colocated authorization in Next.js. Use when centralizing database queries, transforming raw data to DTOs, adding server-only guards, or preventing sensitive data from reaching Client Components. |
| metadata | {"triggers":{"files":["**/lib/data.ts","**/services/*.ts","**/dal/**"],"keywords":["DAL","Data Access Layer","server-only","DTO"]}} |
Data Access Layer (DAL)
Priority: P1 (HIGH)
Centralize all data access (Database & External APIs) to ensure consistent security, authorization, and caching.
Workflow
- Create DAL module in
services/ or lib/data.ts with import 'server-only'.
- Verify auth inside every DAL function using
await auth().
- Transform raw DB/API data into DTOs before returning to components.
- Wrap with
cache() from React to deduplicate requests within render cycle.
- Taint-check sensitive objects to prevent accidental client exposure.
See implementation examples
Implementation Guidelines
- DTOs: Always transform raw data into plain objects. Never return ORM model instances.
- Security: Use
taintObjectReference or taintUniqueValue from experimental taint API to guard sensitive data.
- Authorization: Colocate auth checks inside every DAL function. Never rely on UI layer.
- Caching: Wrap DAL functions in
cache() to deduplicate within single render.
- Error Handling: Throw standardized errors (
NotFoundError, UnauthorizedError) caught by error.tsx or notFound().
Limitations
- Client Components cannot import DAL files. Use Server Actions or Route Handlers as bridges.
Anti-Patterns
- No auth checks outside DAL: Auth verification must live inside DAL functions.
- No raw ORM instances returned: Transform to plain DTO objects before returning.
- No
fetch('localhost/api') in Server Components: Call DAL functions directly.
- No DAL imports in Client Components: Use Server Actions or Route Handlers as bridges.
Canonical response anchors
When this skill applies, preserve the following domain terminology or equivalent concrete examples in the answer when relevant:
