Don't read the answer. Build it. Place servers, caches, queues and shards on the battlefield, wire up the traffic, and defend your design before the god of war himself.
Build a service that turns long links into short ones, then defend it against crowds, distance, collisions, curiosity and bots.
Fan-out on write or on read? Celebrities, ranking and timelines for a billion citizens.
Websockets, presence, delivery receipts and message ordering at scale.
Geospatial indexes, matching riders to chariots, and surge pricing.
Tries, top-k suggestions and sub-50 ms prefix lookups.
Uploads, transcoding pipelines, adaptive bitrate and edge delivery.