Budget Limits
From a contract to a budget
An organisation’s budgets come from what it has bought:
| Step | Calculation | Example |
|---|---|---|
| Annual budget | by contract | 72,000 € |
| Monthly budget | annual ÷ 12 | 6,000 € |
| Daily budget | monthly ÷ 15 | 400 € |
The daily figure is divided by 15, not 30, and that is deliberate. At ÷ 30 you could never use more than an even day’s share, and a deadline or a teaching week would hit the wall. Dividing by 15 gives roughly twice the even daily rate as burst allowance: heavy days are possible, and sustaining that pace all month is not.
Two kinds of budget limit
“Budget limit” covers two mechanisms, and they behave differently. Both are measured in euros;
- A budget cap is a ceiling on a total bill or prepaid credit. Once you reach it you are stopped until the period turns over or an administrator raises it. Your monthly and total budgets are caps. Whatever is left of a monthly budget is carried over and added to the following month’s budget, so nothing you do not spend is lost.
- A budget rate limit is a ceiling on a pace. Once you reach it you are stopped only until the window moves on, an hour later or the next day. It is a throttle rather than a ceiling: nothing is lost by not spending a day’s allowance. There is no rollover here: every new hour and every new day starts from the same limit, whatever was left of the one before.
The four budget limits
| # | Budget limit | Kind | Period | Rollover: is what you did not spend carried to the next period? | Typical default | Response when you hit it | When you can spend again |
|---|---|---|---|---|---|---|---|
| 1 | Total | cap | lifetime of the key or user or organisation | not applicable, a single allowance that never restarts | none set | 429, quoting your usage and your limit | not until an administrator raises it |
| 2 | Monthly | cap | calendar month | Yes, the remainder is added to next month’s budget | €1,000 per user | 429, quoting your usage and your limit | in full, at the start of next month |
| 3 | Daily | rate limit | calendar day, local time | No, every day starts from the same limit | €100 | 429 with a Retry-After header | in full, at midnight local time |
| 4 | Hourly | rate limit | rolling hour | No, every hour starts from the same limit | €20 | 429 with a Retry-After header | gradually, as earlier spending ages out, usually well under an hour |
Defaults are exactly that. Your organisation may set different values.