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

> ## Agent Instructions
> Unkey is two separate products. Compute builds, deploys, and runs apps behind a gateway. API Management issues API keys, enforces rate limits, manages identities and permissions, and reports usage. Say which product a page belongs to; a reader can use either without the other.
> Every Unkey API endpoint is an HTTP POST to https://api.unkey.com/v2/{service}.{procedure} with a root key in the Authorization: Bearer header. Root keys are workspace scoped.
> Error codes have the form err:{system}:{category}:{specific} and each has a page at /errors/{system}/{category}/{specific}.
> The word environment means production or preview in Compute. Rate limiting has four meanings on this site; the glossary lists them.

# openapi_validation_busy

> The gateway is too busy validating requests to check this one right now.

> [!CAUTION]
>
> `err:frontline:capacity:openapi_validation_busy`

The request matches an [OpenAPI validation policy](https://www.unkey.com/docs/compute/gateway/openapi-validation.md), and the gateway is too busy validating other requests to check this one. You get `503 Service Unavailable`.

```json Example response theme={"system"}
{
  "meta": {
    "requestId": "req_3k2j1h0g9f8e7d6c"
  },
  "error": {
    "code": "err:frontline:capacity:openapi_validation_busy",
    "message": "The gateway is busy. Retry shortly."
  }
}
```

Browsers get the same error as an HTML page.

## If you're calling an API hosted on Unkey

Retry after a short delay, with backoff.

## If you own this API

If you see this often under normal traffic, contact support.

## [OpenAPI validation](https://www.unkey.com/docs/compute/gateway/openapi-validation.md)

**Compute docs.** OpenAPI validation policies are a Compute gateway feature.

## Related errors

* [`err:frontline:client:openapi_validation_failed`](https://www.unkey.com/docs/errors/frontline/client/openapi_validation_failed): the request doesn't match the OpenAPI spec.
* [`err:user:bad_request:request_body_too_large`](https://www.unkey.com/docs/errors/user/bad_request/request_body_too_large): the body is over the 4 MiB limit.


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