<h2>Why Zero Downtime?</h2><p>Every minute of downtime costs money and erodes user trust. Modern deployment strategies let you ship code <strong>without taking your application offline</strong>.</p><h3>Blue-Green Deployments</h3><p>Run two identical production environments:</p><ol><li><strong>Blue</strong> serves live traffic</li><li><strong>Green</strong> receives the new deployment</li><li>Once verified, swap the router to <strong>Green</strong></li><li>Blue becomes your instant rollback target</li></ol><h3>Rolling Deployments</h3><p>Update instances <em>gradually</em>, one at a time:</p><ul><li>Works well with container orchestration (Kubernetes, ECS)</li><li>Lower resource overhead than blue-green</li><li>Slower rollback compared to blue-green</li></ul><h3>Database Migrations</h3><p>The trickiest part of zero-downtime deploys is <strong>database changes</strong>. Follow these rules:</p><blockquote><p>Never rename or remove a column in a single deploy. Instead: <strong>add the new column → migrate data → deploy code using the new column → remove the old column.</strong></p></blockquote><pre><code>// Step 1: Add column\nSchema::table('users', function (Blueprint $table) {\n $table->string('full_name')->nullable();\n});</code></pre><hr><p>Pair your deployment pipeline with <strong>health checks</strong> and <strong>automated rollbacks</strong> for maximum safety.</p>