Can I set a billing limit per month?

@michael i remember when fly.io was mentioned on hacker news with this:
(Launch HN: Fly.io (YC W20) – Deploy app servers close to your users | Hacker News)

"
Max monthly spend: unexpected traffic spikes happen, and the thought of spending an unbounded amount of money in a month is really uncomfortable. You can configure fly.io apps with a max monthly budget, we’ll suspend them when they hit that budget, and then re-enable them at the beginning of the next month.
"

so, does this exist or not?