How We Ran Two Portals on the Same Domain During a React Migration (Without User

<p><em>Originally published on <a href="https://tamiz.pro/insights/replacing-dns-resolver-in-production" rel="noopener noreferrer">tamiz.pro</a>.</em></p> <h2> Introduction </h2>

<p><em>This is a submission for the <a href="https://dev.to/challenges/google-cloud-next-2026-04-22">Google Cloud NEXT Writing Challenge</a></em></p> <p>How do you change an

<blockquote> <p>The pager went off at 2:14 AM.</p> </blockquote> <p>If you’ve spent any time operating distributed systems, you know that sound. It doesn’t just wake you up; it

<p>Deploying a new version of your app without kicking users out or causing errors sounds like a dream, right? Let's make it real.</p> <p>The Problem<br /> You git push, run your

<p>In March 2024, Google replaced First Input Delay with Interaction to Next Paint as an official Core Web Vital. FID is gone. INP is what matters now — and most React apps that