Design a geo-proximity service that finds the nearest places to a user, like Yelp or store locators.

Find the 20 nearest restaurants within 5km, fast, for millions of users. A naive distance scan over every place is hopeless. The design is about spatial indexing, geohash or quadtree partitioning, and handling dense cities versus empty regions. Here is how proximity search works.

Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.