Why is my Google Cloud SQL instance being billed every hour?

Question

It seems like I'm being overbilled but I want to make sure I am not misunderstanding how Per Use billing works. Here are the details:

• I'm running a small test PHP application on Google App Engine with no visitors other than myself every once in a while.
• I periodically reset the database via cron: originally every hour, then every 3 hours last month, now every 6 hours.
• Pricing plan: Per Use
• Storage Used: 0.1% of 250 GB
• Type: First Generation
• IPv4 address: None
• File system replication: Synchronous
• Tier: D0
• Activation Policy: On demand

Here's the billing through the first 16 days of this months:

Google SQL Service  D0 usage - hour 383 hour(s) $9.57

16 days * 24 hours = 384 hours * $.025 = $9.60 . So it appears I've been charged every hour this month. This also happened last month.

I understand that I am charged the full hour for every part of an hour that the SQL instance is active.

Still, with the minimal app usage and the database reset 4 times a day, I would expect the charges (even allowing for a couple extra hours of usage each day) to be closer to:

16 days * 6 hours = 80 hours * $.025 = $2.40.

Any explanation for the discrepency?

Answer 1

The logs are the source of truth usually. Check them to see if you are being visited by an aggressive crawler, a stuck task that keeps retrying etc.

Or you may have a cron job that is running and performing work. You can view that in the "task queue/cron jobs" section in the control panel.

Answer 2

You might be have assigned an Ipv4 address to your instance and Google Developer Console clearly states

You will be charged $0.01 each hour the instance is inactive and has an IPv4 address assigned.

This might be the reason of your extra bill.