BorisD,
I did miss it 
thanks a lot!
Topic summary
A developer is working on validating incoming requests to a custom Shopify app with a proxy endpoint. They initially tried to use the x-request-id and x-request-sign headers to verify request authenticity.
Resolution:
- Another user clarified that signature validation should use URL query parameters, not headers
- The official Shopify documentation on calculating digital signatures for app proxies was provided as the solution
- The original poster confirmed this resolved their issue
Follow-up question:
A third user asked how to access the x-request-id header within the app proxy, which remains unanswered.
The discussion appears resolved for the original question, though the follow-up query about header access is still open.