System designLevel 3
Real-time systems
Easynot started
Mediumnot started
Hardnot started
Geospatial & location systemsFinding the closest driver to a rider without scanning the entire planet.3 minGraph database shardingWhy breaking a social network across multiple servers is an architectural nightmare.3 minAnycast edge routingOne IP address, many physical servers worldwide.3 minDNS traffic routing (gateway)Using DNS to balance load across entire continents.3 minEdge realtime syncMaking multiplayer apps feel instant, even across the world.3 minImage and video delivery (CDN + transformations)Why serving images directly from your own database is a massive architectural anti-pattern.3 minMQTT: the IoT broker protocolTiny devices don't talk to each other directly, they publish to topics, and a broker fans each message out to whoever subscribed.4 minMulti-region traffic failoverWhen a whole region goes dark, the gateway notices through health checks and reroutes users to a region that's still healthy.4 minRead replica routingDirecting traffic to save the Primary Database from exhaustion.3 minShort polling for presenceClients keep asking the server "anything new?" on a fixed clock, instead of being told.4 minSIP session routingBefore any audio flows, a chain of SIP messages negotiates the call path between caller, proxies, and callee.3 minTLS ingress protocol routerOne public address, many services behind it, the ingress peeks at the hostname inside the TLS handshake and sends each connection to the right backend.3 minURL routingA router is a guard that tries each pattern in order and hands the request to the first one that fits, pulling out the variable bits.3 minVPN tunnel service protocolWrap a private packet inside a public one so it can cross an untrusted network sealed and unread.3 min