docker-multi-stage-stack-builderlisted

# Docker Multi-Stage Stack Builder ## 1. System Architecture & Prerequisites This skill builds a complete production stack: a **multi-stage Next.js Docker image** (<100MB target), **PostgreSQL**, **Redis**, and an **Nginx reverse proxy** — all orchestrated via Docker Compose with health checks, volume persistence, and dependency ordering. **Architecture layers:** ``` [Client] → [nginx:1.27-alpine] → [next-app:standalone] → [PostgreSQL 16] + [Redis 7] ``` **Prerequisites:** - Docker ≥ 24 & Docker Compose V2 (`docker compose` plugin) - Node.js ≥ 18 (for local development only) - A working Next.js project with `output: "standalone"` in `next.config.ts` ## 2. Input/Output Data Contracts **Input — Environment Variables (.env.example):** ```json { "$schema": "http://json-schema.org/draft-07/schema#", "type": "object", "required": ["POSTGRES_PASSWORD", "NEXTAUTH_SECRET"], "properties": { "POSTGRES_USER": { "type": "string", "default": "appuser" }, "POSTGRES_PASSWORD": { "type": "string", "description": "Strong password for PostgreSQL" }, "POSTGRES_DB": { "type": "string", "default": "appdb" }, "DATABASE_URL": { "type": "string", "description": "Full postgres:// connection string" }, "REDIS_URL": { "type": "string", "default": "redis://redis:6379" }, "NEXTAUTH_SECRET": { "type": "string", "description": "Auth secret for Next.js" }, "NEXTAUTH_URL": { "type": "string", "default": "http://localhost:3000" }, "NODE_ENV": { "type": "string",