angular2 async http requests

Question

May be I don't understand how async requests should work, but from my point of view 1 ajax or 10 should took almost the same time to be finished. Right now I'm facing a problem, I'm sending 3 ajax requests at the same time, and it took about 3 seconds for the first ajax, 15 seconds for the second, and 18 for the last. But if I send only first ajax - it's took 3 seconds, only second - 15 seconds, only third - 1 second. So, in other words it doesn't matter if I send 3 ajax together

this.contractService.saveContractsForOpportunity(selectedContracts).subscribe(data => {

});
this.contractService.saveContractsForOpportunity(selectedContracts).subscribe(data => {

});
this.contractService.saveContractsForOpportunity(selectedContracts).subscribe(data => {

});

Or if I send it one by one like this

this.contractService.saveContractsForOpportunity(selectedContracts).subscribe(data => {
    this.contractService.saveContractsForOpportunity(selectedContracts).subscribe(data => {
       this.contractService.saveContractsForOpportunity(selectedContracts).subscribe(data => {

       }); 
    });        
});

It tooks the same time to be finished

May be it's only about backend or server configuration?

Answer 1

Most likely your problem lies on the server side. Does the server allow handling multiple requests from the same IP in parallel?