Best way to store large geo-tagged data? [on hold]

I am developing a web-app which will run on Google app-engine(GAE).

I need to store a reasonably large (few million entries) dataset, with each entry consisting of a data-point descriptor, a lat-long location info and date-time info. I plan to overlay this on Google Maps by querying and retrieving data-points within a certain circle of certain radius from the user's location. The large data-set will be dynamic.

What would be the best way to implement this on GAE?