Performance issue with Global search option

We are using Global search option in an skuid page which has multiple models. While searching through the global search option it makes call to multiple API's and salesforce data.The problem is while searching for the first time i.e First search,its taking 5-15 minutes but later search happens in 15-25 seconds. We are not able to find why the first search takes so long?
It would be great if anyone help us in solving this issue.

Thanks in advance!