https://sohilladhani.com/blog/tags/infrastructure/Recent content in Infrastructure on Sohil Ladhani BlogHugoen-usSat, 25 Jul 2026 00:00:00 +0000https://sohilladhani.com/blog/post/2026-07-25-anycast-and-pop-placement/Sat, 25 Jul 2026 00:00:00 +0000https://sohilladhani.com/blog/post/2026-07-25-anycast-and-pop-placement/Cloudflare has 300+ Points of Presence (PoPs) globally. When you make a request to a Cloudflare-protected site, you don’t connect to a server in a specific city — you connect to the nearest Cloudflare PoP, wherever that is. This works via anycast: multiple servers worldwide share the same IP address, and BGP routing delivers your packets to the geographically closest one. PoP placement and anycast are the foundation of how CDNs achieve global low latency.https://sohilladhani.com/blog/post/2026-07-23-dns-based-traffic-routing/Thu, 23 Jul 2026 00:00:00 +0000https://sohilladhani.com/blog/post/2026-07-23-dns-based-traffic-routing/DNS returns an IP address. It doesn’t have to return the same IP address every time. The authoritative nameserver can return different IPs based on where the query originated, which backend is healthy, or how much traffic each backend should receive. DNS-based traffic routing uses this flexibility to implement geographic routing, load balancing, and failover without changing a line of application code. GeoDNS The recursive resolver’s IP address reveals the approximate location of the client (or at least the ISP).https://sohilladhani.com/blog/post/2026-07-22-dns-resolution/Wed, 22 Jul 2026 00:00:00 +0000https://sohilladhani.com/blog/post/2026-07-22-dns-resolution/Every system design interview starts with a client making a request. Before that request reaches your load balancer, DNS has already run. DNS translates api.example.com into an IP address. It’s a globally distributed read-heavy system that handles 3.5 trillion queries per day. Understanding how resolution works explains why DNS changes take time to propagate and how DNS-based traffic routing is possible. The Resolution Chain A DNS query for api.example.com follows a chain of four server types: