The original title is: "NestJS Zero-Downtime Deployment on DigitalOcean with GitLab CI/CD and PM2"

Short summary

Complete production guide to deploying NestJS backends with true zero downtime on DigitalOcean. Uses PM2 in cluster mode with ready-signal handoff, Nginx as reverse proxy with keepalive connections, and fully automated GitLab CI/CD with lint, test, build, and deploy stages. Covers entire stack: Droplet Ubuntu setup, SSL/TLS via Certbot, non-root deployer user security, PM2 configuration with graceful reload semantics, and tested GitLab pipeline with artifact caching.

• •Deploy NestJS with zero downtime using PM2 cluster mode and Nginx reverse proxy with ready-signal handoff
• •Complete automated GitLab CI/CD pipeline with lint, test, build, and deploy stages using artifact caching
• •Production security & gotchas covered: non-root deployer user, Node.js direct installation (avoid nodesource), Husky prepare hook handling

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