Is the 504 Gateway Time-out error ok?

Link: https://infogram.com/api/merge/auth/google/?redirect_to=123&token=gulHMyL6-1H0Am4zXa4H7j0DWomPdnKPhZOk&redirect_to=123 it gives 504 after a long time! Is it normal? It can be used for DOS! I use two redirect_to= if I use just one redirect_to= it gives the response fastly! https://infogram.com/api/merge/auth/google/?redirect_to=123&token=gulHMyL6-1H0Am4zXa4H7j0DWomPdnKPhZOk ## Impact DOS?