Debug “App Can’t Reach Private Database” Boundary by Boundary
Debugging a private database connection means testing DNS, routing, filtering, workload identity, and database authorization one boundary at a time. This hands-on troubleshooting lesson matches storefront timeout evidence to the boundary it narrows. Covers: DNS lookups from the workload network, asymmetric return routes, security groups, SYN timeouts versus TCP resets, authentication versus authorization errors, safe mitigations. Practice: What boundary does this evidence point to? Prerequisites: Private endpoints and private DNS.
We'll cover the following...
The Storefront API tier is timing out during a seasonal traffic spike. Some connections fail intermittently, and the incident note says private endpoints were enabled yesterday. That change is a clue, not a diagnosis. A timeout describes missing progress on a connection attempt, while a database authentication error shows that traffic reached a database listener and failed at a later boundary.
Let’s begin with the first discriminating test, a Domain Name System (DNS) lookup from the API workload network. We will test separate hypotheses in order: DNS mis-resolution, route or return-path failure, network filtering, workload identity, and database authorization. ...