How calculate the number of instances in Google App Engine

Question

I aim to create an application that will be deployed thanks to Google App Engine.

Before that I would like to calculate the cost of Google App Engine.

For this I

Answer 1

It's really hard to answer without more info. App engine consumption will depend on the nature of your app, the average session span and usage hours, how well you optimize your implementation and so much more variables...

Don't think about how many instances, think about how many instance hours you'll need to serve your users if you can figure how much you'll be consuming you could get an estimate using the App engine pricing calculator .

Answer 2

Completely depends on the code that runs on each request. You need to make it more specific to get a better answer. Ive had carefully implemented apps that receives thousands of requests per minute with a single instance. How long each request takes and the memory it consumes is key as well as the frontend instance type you select to use.
Appengine also lets you calibrate some parameters like min/max latency to control when more instances are launched.