# Rate limits

Source: https://parasend.com/docs/rate-limits

There is no fixed limit on requests per second for an API key today. Send at the pace your work needs. To send many deliveries at once, use a [batch](/docs/api/batches) rather than thousands of single calls: one request, and Parasend paces the notices.

Some actions have limits of their own. Each answers `429` with a code that says which limit was reached:

| Limit | Code | What to do |
|---|---|---|
| The key's monthly cap of deliveries, if you set one in **API keys** | `monthly_delivery_cap_exceeded` | Raise the cap in the portal, or wait for the next month. |
| The free plan's daily number of deliveries | `free_daily_cap_reached` | Choose a plan in the portal, or wait until tomorrow. |
| Your monthly spending cap, if you set one | `spending_cap_reached` | Raise the cap in the portal, or wait for the next month. |
| Manual reminders: 10 per recipient a day | `remind_rate_limited` | Try again tomorrow. Automatic reminders from the [follow-up policy](/docs/api/follow-up-policies) do not count. |
| The [record check](/docs/api/verify/check): 120 lookups an hour from one address, and 20 lookups that find nothing in 10 minutes | `rate_limited` | Wait the seconds in `Retry-After`. |

Limits on test-mode deliveries follow the key's own cap only: test mode is never billed, so the free and spending limits do not apply to it.

## Headers

An endpoint with a fixed limit, such as the record check, tells you where you stand on every answer:

| Header | What it says |
|---|---|
| `RateLimit-Limit` | How many requests the window allows. |
| `RateLimit-Remaining` | How many are left in this window. |
| `RateLimit-Reset` | Seconds until the window starts again. |
| `Retry-After` | On a `429`: seconds to wait before trying again. |

## Handling a 429

Wait as long as `Retry-After` says when it is there; otherwise back off exponentially, starting at one second. Retry a `POST` with the same `Idempotency-Key`, so a retry can never send twice. A `429` for a cap or a plan limit will not clear by waiting a few seconds: the code says which it is, so show it to a person instead of retrying in a loop.