How to Build a Real-Time Notification System for a Classified Marketplace: Archi

<p>You open amazon.com. A product page loads in under a second. Behind that single page load, your request hit a DNS server, bounced through a CDN edge node, passed a rate

<p>API design patterns<br /> API event architecture<br /> API integration strategies<br /> API latency comparison<br /> API performance optimization<br /> API resource

<p>I got an email from Vercel.</p> <p>"You've used 75% of your free plan resources."</p> <p>I ignored it.</p> <p>A few hours later, I was at 100%.</p> <p>I'd been building

<blockquote> <p><strong>Who is this for?</strong> Mid-to-senior engineers preparing for system design interviews, or anyone curious how a short-video platform at billion-user

<p>Most applications don't fail because of bad code.</p> <p>They fail because of bad architecture decisions made early that nobody questioned <br /> until it was too late.</p>

<p>Modern applications thrive on instant updates — from live chats and notifications to collaborative tools and trading dashboards. Traditional HTTP requests can only go so far

<h2> 1. Intro — The Problem We Actually Had </h2> <p>Building real-time systems is often presented as a distributed systems problem.</p> <p>Kafka, stream processors, event buses,

<p>Most developers underestimate how hard messaging systems really are.</p> <p>A basic chat demo with WebSockets is easy to build. A production-grade messaging platform like