> ## Documentation Index
> Fetch the complete documentation index at: https://docs.invoca.com/llms.txt
> Use this file to discover all available pages before exploring further.

# RingPools Sizing Logic

> Auto-scaling automatically adds numbers to a RingPool as traffic grows and removes unused numbers at the end of each billing cycle.

Promo numbers are a limited and valuable resource, which is why most Invoca accounts automatically manage the quantity of numbers in a RingPool through auto-scaling. Auto-scaling can both add numbers to improve call attribution and remove numbers automatically so you're not billed for ones you don't use.

When a landing page receives enough visitors quickly enough to use up all the promo numbers in a RingPool, two things happen:

1. Instead of a unique promo number, a visitor sees a different number based on your settings — either an overflow number (which still tracks and routes the call, but without personalized attribution) or the original destination number (with no tracking or attribution at all).
2. If enabled, auto-scaling automatically adds more promo numbers to the RingPool, which are shown to subsequent visitors instead of the overflow number — even if a visitor never actually calls that number.

Auto-scaling also removes unused numbers automatically: at the end of each month, it removes unused promo numbers from your RingPool before your next billing cycle begins.

## Enabling auto-scaling in your account

Auto-scaling is enabled for most accounts, including all new ones. To check whether your RingPools have it enabled, contact your Invoca Account Manager, or have a Super User follow these steps:

1. Log in to Invoca. In the sidebar menu, click **Settings**.
2. In the Network section, if you see RingPool Auto-Scaling, it's enabled for your account. Click it to edit your settings.
3. From there, you can enable auto-scaling for each new RingPool you create, and choose whether those RingPools include an overflow number.

If you don't see the Auto-Scaling option and want it enabled, reach out to your account team or [support@invoca.com](mailto:support@invoca.com).

## FAQs

**Why am I still receiving overflow calls if my RingPools are increasing automatically?**
By default, auto-scaling adds only one new promo number every five minutes. During a sudden traffic surge, it may take several minutes for your RingPool to reach the right size.

**Why are my RingPools increasing if I didn't receive any overflow calls?**
Auto-scaling triggers whenever an overflow number is *presented* on your landing page, whether or not it's actually called — this maximizes the number of visitors assigned unique promo numbers.

**Does auto-scaling work with local phone numbers?**
Yes. For a local number RingPool, auto-scaling tries to grow with a number from the same location first, falling back to a toll-free number if none are available locally.

**Can I enable auto-scaling only for some campaigns?**
Yes — the same settings menu described above lets you apply auto-scaling to only certain campaigns or destination numbers.

**How does auto-scaling remove unused promo numbers?**
Each night, auto-scaling marks the least recently called numbers in an eligible RingPool as "Reserved" — held as standby capacity rather than removed immediately (see [What Is a Reserved RingPool Number?](/s/article/what-is-reserved-ringpool-number)). On the last day of each month, auto-scaling checks those Reserved numbers and removes any that still qualify as unused, so you aren't billed the following month. A number is considered unused if it hasn't been shown to a visitor in the past 5 days or received a call in the past 10 days. If a RingPool has shown an overflow number in the past 30 days, it doesn't scale down at all. Auto-scaling never removes more than 20% of a RingPool's numbers in a single month.

## Where to go next

* [RingPool Auto-Scaling](/s/article/ringpool-auto-scaling)
* [RingPool Quality Protection](/s/article/ringpool-quality-protection)
* [What Is a Reserved RingPool Number?](/s/article/what-is-reserved-ringpool-number)