# Next.js Data Access Layer

> Secure, reusable data access patterns with DTOs and Taint checks.

- Skill: `fierzone/next-js-data-access-layer` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add fierzone/next-js-data-access-layer`
- Raw SKILL.md: https://api.skillmd.com/api/skills/fierzone/next-js-data-access-layer/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Web & Frontend
- Author: fierzone (https://skillmd.com/u/fierzone)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/fierzone/next-js-data-access-layer

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# Data Access Layer (DAL)

## **Priority: P1 (HIGH)**

Centralize all data access (Database & External APIs) to ensure consistent security, authorization, and caching.

## Principles

1. **Server-Only**: Must include `import 'server-only'` to prevent Client bundling.
2. **Auth Co-location**: Auth checks (`session.role`) must be **inside** the DAL function.
3. **DTO Transformation**: Return plain objects (DTOs), never raw ORM instances.
4. **No Internal Fetch**: Call DAL functions directly. Do not `fetch('localhost/api')`.

## Implementation

| Approach              | When to use                                      | Reference                           |
| :-------------------- | :----------------------------------------------- | :---------------------------------- |
| **API Gateway (BFF)** | Enterprise apps with separated Backend (NestJS). | [Pattern A](references/patterns.md) |
| **Direct DB**         | Fullstack apps or Admin Panels.                  | [Pattern B](references/patterns.md) |

## Limitations

- **Client Components**: Cannot import DAL files. Must use Server Actions or Route Handlers as bridges.