Originally published to dakotalewallen.me
Billing in AWS can feel intimidating. Rightfully so given that it is a pay-as-you-use model. Trading the guarantees of a contract for agility. Because of this, there are plenty of stories of people getting a bill that far exceeds what you were expecting. So here's what you can do to avoid being another one of those stories.

In the AWS console, navigate to the billing dashboard

Then you will want to go to the Budgets dashboard

From here you'll want to click on Create Budget and fill out the form like so to get started. You'll need an email and an ideal dollar amount you would like to alert against.

After you've created your budget. Click into it and go to the upper right hand corner where you will see an Alerts section. Click on View all Alerts. Here's where the magic happens.

By default this will provide you with three alerts.
1.) Actual cost > 85%
2.) Actual cost > 100%
3.) Forecasted cost > 100%

You can think of cost like a bucket associated with your account. As you use services within AWS they will pour cost into the accounts bucket.
Actual Cost means that your bucket has been filled up to a certain point
Forecasted Cost means that based on the rate of cost coming in, we expect you to incur X this month.

Both are super important. But for the case of monitoring against spend, you typically will want to alert against Forecasted costs not actual. That way you can use it as a predictive measure rather than a reactive one.

So the first three alerts provide you some lead in up to your point. But not much past that. To set that up you will need to click on the Edit Alerts button. Once on that page scroll to the very bottom and you'll see a Add alert threshold button.

You will be greeted with an empty threshold form. You should enter a percentage greater than 100, and set the trigger to Forecasted. This way you will be alerted once the account spend is set to exceed a certain amount past what you predicted. Finally you'll supply an email for the alert to.

You now have configured billing alerts for your account that will lead up to a set amount. As well as a relative amount past that.

Best of luck and hope this helps.

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