Golang and Redis assignment -- 2

Golang - Problem statement At our eCommerce company we are using a mapping service, lets say google maps or open street maps for reverse geo location i.e from lat,lng of a user get his address. From his full address we are mainly using pin code, and not the actual address. So for us pincode is only important. Since we are getting a huge amount of traffic we cannot always use maps api, as there is always a cost associated with calling the map api. So we need to start caching data. Since we are operating in fixed amount cities, we can ideally build our own internal database of lat,lng to pincode mapping. This way we don't need to always call map api and we can reduce costs over time. Proposed solution 1. Store lat, lng of user to his pincode in redis. [login to view URL] 2. Define a threshold, lets say 1km inside which we assume that pincode won't change. 3. When we want to rev geo code, we first check if we have pin code already available in redis cache and we simply show user pin code from our cache. Using this function [login to view URL] See if you can build a service to implement this. Also think of any edge cases which might break in the above solution, and any workarounds for the same