Content-Location

A successful QUERY response may name a GET-able resource that represents the same result. Set it in your handler:

app.query('/search', async (request, reply) => {
  const { id, results } = await runSearch(request.body)
  reply.header('content-location', `/search/results/${id}`)
  return results
})

This lets a cache revalidate via GET /search/results/<id> instead of re-sending the original QUERY body, and matches the convention a client already understands for GET responses.

When to use it

• The result is stable enough to be addressable as its own resource (a saved search, a paginated view, a materialized query).
• You want clients and intermediaries to be able to bookmark, link to, or share the result.

When to skip it

• The result is ephemeral and only meaningful with the original query body.
• You do not have (or do not want to expose) a GET-able representation.

The spec describes this as a MAY — the field is optional.