How would you do a blue-green deployment with Nginx?

Blue-green reduces deployment risk by keeping the previous version running while the new version receives traffic. Nginx's role is to switch upstreams atomically and reload without dropping in-flight requests.

upstream app {
    include /etc/nginx/upstreams/app-active.conf;
}

server {
    location / {
        proxy_pass http://app;
        proxy_next_upstream error timeout http_502 http_503;
    }
}

Safe switch sequence

• Deploy the green environment and run smoke and health checks before sending user traffic
• Update the include file atomically, run nginx -t, then reload
• Watch error rate and latency while old workers drain in-flight requests
• Keep blue running until the rollback window closes, then scale it down
• Make database migrations backward compatible so both versions can run at once
• Use sticky sessions only when necessary; shared session storage is easier to switch