System design interview question
"Design Google Maps. Focus on two things: serving the map itself to a billion users, and computing driving directions between any two points on Earth with live traffic. 1 billion users, 20 billion route requests a day."
graph algorithms at planetary scale, which is unusual in system design. The key realization is that plain Dijkstra over a continental road network (hundreds of millions of nodes) takes seconds — far too slow — so the system must use precomputation and hierarchy to answer in milliseconds. The tile-serving half is a separate, much easier caching problem.
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