How to display a layer using coordinates?

Question

PostgreSQL

Hello!
There is a task by location to show which municipal deputy of the district. While we will do in one city:
- Constituency. draw or find yourself. ID county
- send api coordinates. get response ID of county
Conditionally:
SendCoordinates : {
"latitude": 54.734015,
"longitude": 55.967808
}
Response:
YourDeputy:
{id:23,
city: Ufa,
okrug: Constituency 7}
What is the easiest and most economical way? Maybe there are web services?