[mynameisash]

> For deciding if a user is in Texas you could create a simple polygon completely inside Texas and one in Oklahoma.

This seems like the obvious optimized v1: create extremely compressed (simplified) polygons wholly within the proper geopolitical borders. You get 100% true positives for a significant fraction of queries, and any negatives you can still kick to GMaps. I understand wholly-local is the goal here, but as others have pointed out, even small error rates can be unacceptable in some scenarios.

[zeke]

Yes, just paying for the between spots is exactly what I thought later in the day. Then check every month which areas cause costs and add those to the in-house polygons.