Networking & Infrastructure
Also known as: Domain Name System
A hierarchical, distributed naming system that translates human-readable domain names like systemcity.io into IP addresses computers route to.
The Domain Name System is the phonebook of the internet. When a client wants to reach systemcity.io, it asks a DNS resolver, which walks a hierarchy of name servers — root servers, top-level-domain servers (.io), and the authoritative servers for systemcity.io itself — to find the IP address. Results are cached at every level (browser, OS, recursive resolver, intermediate caches) to make subsequent lookups fast.
DNS is also a powerful traffic-routing tool. Round-robin DNS returns multiple A records to spread load. Geo-DNS returns different IPs based on the client's location, sending users to the nearest data center. Failover DNS removes IPs of unhealthy regions. Anycast DNS routes the same IP to many physical locations and lets BGP pick the closest. Modern systems combine these (Route 53, Cloudflare, NS1) for global traffic management.
DNS-based decisions are bounded by TTL (time to live). A short TTL (60 seconds) lets you fail over quickly but increases lookup load. A long TTL (1 hour) is efficient but slow to react to outages.
Use DNS-level load balancing for global traffic distribution, regional failover, and as the first layer of routing in a multi-region architecture.
DNS caching makes changes slow to propagate. TTL is a blunt tool — clients ignore it inconsistently, and intermediate resolvers add their own caching.
A globally distributed network of edge servers that cache static content close to end users to minimize latency and origin load.
A component that distributes incoming network traffic across multiple backend servers to maximize throughput, minimize response time, and avoid overload.
The time delay between a request being sent and a response being received — typically measured in milliseconds.
A server that sits in front of one or more backend servers and forwards client requests to them, often handling TLS, caching, compression, and load balancing.
TCP is a reliable, ordered, connection-oriented protocol. UDP is a fast, connectionless, best-effort protocol. They serve different workloads.
A major revision of the HTTP protocol that introduces multiplexing, header compression, and server push over a single binary framing layer on TCP.