Rails request timeout on browser but backend still works

I have Zone, Location and Capacity models such that, zone has_many :locations and location has_many :capacities.
On my rails4 production server, when I try to create more than 500 locations with capacities, it times out and shows 500 error. But on the backend, it keeps creating the locations with capacities. How can I stop my server from timing out and know when the backend process is complete.
PS: I am using Nginx on linux environment.