how is Billing for Channel API done?

Question

I've chosen google-app-engine because of its scalability, and now I try to understand how much I will have to pay once I release the product.

I've looked back and forth in the google app engine documentation to find an answer for question and couldn't find. I found few details in the "Quotas" page, I found how much I can get for free and how much is the Billing Default Quota.

In Billing Page there are number for CPU, etc with Resource and Unit and how much it cost. But no where could I find how much will it cost me per channel calls/created, etc.

I can't even try to make calculations with what's in the Admin console, because the current numbers there now are 0 (since there are 2 users which are the programmers).

How can I be ready for the releasing of the product that (hopefully) will have a huge number of channels created daily?

Is there a page I missed, or is there a tool for calculating?

Thanks!

EDIT: Moishe, thanks for the quick and readable answer. So here are some more questions: 1. Do you think - if needed - that I will be able to get even more quota for the number of channels? I saw there's a special form to ask for more quotas, but I'm not sure that includes the Channel-API feature... 2. Are there any posts you've made for "how to use channel-API efficiently"? I saw some stuff about reusing the tokens per user. Is there more?

Thanks again.

Answer 1

Creating a channel costs about 2.7 CPU-seconds. A CPU-hour costs $0.10. So, each channel created costs

(2.7 / 3 600) * $0.10 = $7.5 × 10^-5

So creating 1000 channels will cost $0.075, or 7.5 cents.

You'll also get charged the normal outgoing bandwidth costs for any data sent over a channel.

The CPU cost probably isn't the biggest concern; you're more likely to run into quota caps then running out of money. Paid apps are limited to 86400 channel creations/day (1/second).