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

# Caching

> Use HTTP validators without confusing cache age and source age.

Honor the `Cache-Control` value on each response. Inventory-sensitive responses generally have shorter client cache periods than catalog or store metadata.

Retain the response `ETag` and send it as `If-None-Match` when revalidating:

```bash theme={"dark"}
curl "https://API_HOST/v1/products/by-sku/347210" \
  -H 'If-None-Match: "PREVIOUS_ETAG"'
```

A `304 Not Modified` response has no body. Continue using the representation associated with that validator.

`If-Modified-Since` is available as an HTTP-date fallback when an integration cannot retain ETags. If both validators are sent, `If-None-Match` takes precedence, as required by HTTP semantics. `Last-Modified` is the Nektir publication time—not proof of when Utah DABS last changed its source data.

`X-Publication-Revision` identifies the immutable Nektir database revision used to create the response. It is not a Utah DABS version or upstream update timestamp.

API response caching and upstream polling are separate systems. Revalidating this API does not trigger an upstream refresh.