Why can't I enable Performance Insights on existing instance?

This is indeed a documentation error. Performance Insights relies on the use of PERFORMANCE_SCHEMA, which has a large memory footprint. This is why micro and small instances are not supported. The documentation will be updated to align with what is actually supported.

Hello, I've reviewed the document and it appears that your design should be compatible with Performance Insights. However you might not able to see them due to possible reasons

1. The feature may not be available in your region. Refer to this document to check the availability https://aws.amazon.com/about-aws/whats-new/2021/10/rds-performance-insights-more-regions/

2. Your RDS instance may not be running with sufficient permissions to access Performance Insights. Refer to this document to check the necessary IAM permissions. https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_PerfInsights.access-control.html

3. The Performance Insights feature may be disabled at the parameter group level. Check this document for further information https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_WorkingWithParamGroups.html

4. Finally, it can take some minutes to appears, if you were just created the RDS. Refer to this document https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_PerfInsights.Enabling.html

@AWS please update documentation. t4g is not supported even with latest version of mariadb.

Hello there,

We're sorry to hear about the trouble you've faced, but are thankful for you bringing this to our attention.

I've forwarded this information to our service teams for review. Please feel free to share any feedback related to our documentation directly to us, via the 'Provide feedback' button at the bottom of the related docs page.

Regards,

-- Ben G.