# Mern Stack > Stack decisions for MERN apps (Next.js, pnpm monorepo). Reference before scaffolding or architecture work. Use when this capability is needed. - Skill: `tomevault-io/mern-stack` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/mern-stack` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/mern-stack/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Web & Frontend - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/mern-stack --- ## Locked decisions | Layer | Decision | | ------------ | ----------------------------------------------- | | Monorepo | pnpm workspaces | | Frontend | Next.js (app router), TypeScript required | | API | Next.js route handlers (`app/api/`) by default | | Database | MongoDB + Mongoose | | Validation | Zod (shared schemas in `packages/shared`) | | Environments | local → non-prod → prod | | Secrets | `.env.local` for dev; AWS for production | | Containers | Not required unless deployment target forces it | ## Project layout ``` apps/web/ # Next.js app app/api/ # API route handlers src/server/ # Server-only code packages/shared/ # Zod schemas, types, utilities .github/workflows/ # CI/CD (root configs) # eslint, prettier, tsconfig ``` ## When to add a separate API service Only justified if: - Long-running jobs exceed serverless timeouts - WebSocket/persistent connections required - Shared API serves multiple non-Next.js clients - Compliance requires API isolation Default: keep API in Next.js route handlers. ## Reference For versions, env setup, and deployment patterns, see `reference/mern-stack-reference.md` --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/edfenton) — claim your Tome and manage your conversions.