using Haversine formula find the scope min longitude - max longitude, min latitude - max latitude
advantage: without any package or database
disadvantage: poor performance
Using Redis for caching and saving location Redis Geospatial is a module for processing geospatial data
Even with billions of data, only the first time query will query the database, after the first time query saves the cache Redis will respond ASAP Should also do data persistence in case of redis restart
Depending on the system QPS may need a redis-cluster in the future
advantage: good performance, fast response disadvantage: extra cost, extra learning cost
