Troubleshooting entry for missing index page and "Cannot GET /" (#2132)

Co-authored-by: Christian Georgi <[email protected]>
Co-authored-by: Mahati Shankar <[email protected]>
Co-authored-by: Christian Georgi <[email protected]>
Co-authored-by: René Jeglinsky <[email protected]>

Author: 4 people

get-started/troubleshooting.md

@@ -626,8 +626,7 @@ Now you can build the archive with:
 mbt build -t gen --mtar mta.tar -e less.mtaext
 ```
 
-::: warning
-This approach is only recommended
+::: warning Not recommended for production deployments
 - For test deployments during _development_.  For _production_ deployments,  self-contained archives are preferrable.
 - If all your dependencies are available in _public_ registries like npmjs.org or Maven Central.  Dependencies from _corporate_ registries are not resolvable in this mode.
 :::
@@ -768,7 +767,16 @@ If you receive an error response `404 Not Found: Requested route ('<route>') doe
 
     :::
 
+### Why do I get a _404 Cannot GET /_ error?
 
+For security reasons, the **index page is not served in production** by default in both [Node.js](../node.js/cds-server#toggle-generic-index-page) and [Java](../java/developing-applications/configuring#production-profile).
+
+If you try to access your backend URL, you will therefore see a _404 Cannot GET /_ error.
+This also means you **cannot use the `/` path as a health status indicator**.  See the [Health Checks guide](../guides/deployment/health-checks) for the correct paths.
+
+Only if absolutely required and you understand the security implications to your application, you can enable this page in your deployment.
+
+Learn more about the generic index page in [Java](../java/developing-applications/properties#cds-indexPage) and in [Node.js](../node.js/cds-server#toggle-generic-index-page).{.learn-more}
 
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