I just completed the "Deploy an Amazon RDS Multi-AZ and Read Replica in AWS" lab in the course. I think the section where you update the CNAME record is misleading. I wanted a more realistic experience so I stopped the "primary" instance. This led the WordPress site to return a 504 (expected). However, when I updated the CNAME to the read replica’s endpoint I continued to get a 504. I’m pretty sure this is because the TTL on the record is 900 seconds (15 minutes). This means that most students working through the lab will never actually see the read replica become the new primary.
Is my understanding here correct? Is this a known issue?
Hmm even after waiting a while it’s not working. I don’t have the time to dive in but I think something is wrong here.