> For the complete documentation index, see [llms.txt](https://docs.enclaive.cloud/virtual-hsm/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.enclaive.cloud/virtual-hsm/troubleshooting/allow-if-modified-since-requests.md).

# Allow If-Modified-Since Requests

This health check ensures optimal header configuration for efficient caching and improved client-side performance by validating the presence of the `If-Modified-Since` and `Last-Modified` headers.

**Health Check Name: `allow_if_modified_since`**

#### **Accessed APIs**

| Method | Endpoint                  | Description                                    |
| ------ | ------------------------- | ---------------------------------------------- |
| READ   | `/sys/internal/ui/mounts` | Reads mount configuration for secrets engines. |

#### **Configuration Parameters**

| Parameter | Default | Description                 |
| --------- | ------- | --------------------------- |
| None      | N/A     | No configurable parameters. |

#### **Health Check Results**

| Condition                                                         | Status             |
| ----------------------------------------------------------------- | ------------------ |
| Both headers (`If-Modified-Since` and `Last-Modified`) configured | OK / Informational |
| Only one header configured                                        | Warning            |
| Neither header configured                                         | Informational      |

This check validates if:

* `If-Modified-Since` is included in `passthrough_request_headers`
* `Last-Modified` is included in `allowed_response_headers`

#### **Recommended Actions**

To resolve warnings or improve configuration, update your secrets engine mount settings using the following:

{% hint style="info" %}
**Note:** Replace `<mount>` with your actual secrets engine mount path.
{% endhint %}

**Standard Configuration**

```bash
vhsm secrets tune \
  -passthrough-request-headers="If-Modified-Since" \
  -allowed-response-headers="Last-Modified" \
  <mount>
```

**ACME-Specific Configuration&#x20;*****(If you're using ACME)***

```bash
vhsm secrets tune \
  -passthrough-request-headers="If-Modified-Since" \
  -allowed-response-headers="Last-Modified" \
  -allowed-response-headers="Replay-Nonce" \
  -allowed-response-headers="Link" \
  -allowed-response-headers="Location" \
  <mount>
```

***