The problem is that the view is not indexed when you add documents to it. It uses lazy initialization, so when you access the 1.5M view, it could take for a long tim for the first time.
The nodejs is waiting for some time while view index is build, but it takes longer than expected. You can try to open view's URL in browser to see how long does it take for the first time and for the second one.
So in your situation is is important to optimize the view's map and reduce function for performance.
It is a known issue, but just in case: if you have 1.5M docs, you can forget about reduce functions. Only build-in ones will work fast enough.