AdvancedCloud Networking← All practice

Outbound Calls Time Out While Every Health Check Is Green

The report, in their words

Between 12:00 and 12:40 the checkout service fails about one payment in six with ETIMEDOUT calling the payment provider. Every dashboard is green: instances healthy, all load balancer targets healthy, CPU 35%, database fine, error budget barely moving. The provider says the requests they receive all succeed — they just receive fewer than we say we sent.

Pull evidence

One item at a time, and nothing here tells you which one matters. Deciding what is worth looking at is most of the diagnosis.

NAT gateway metrics
What the health checks actually traverse
Connection state on an application instance
The 11:52 release
What the provider hostname resolves to
The provider's view of our traffic
Instance-level resources
Routes and security groups
Request volume

0 of 9 inspected. You are not required to open all of them — a real investigation is judged on how few you needed.

What is your diagnosis?

Commit to one. Nothing below is shown until you do.

Guessing wrong and being told exactly why is the point of this page. Reading the answer first is not practice.