Aws RDS postgre multi-az db cluster - Failling add s3 lambda role

Question

I'm trying to setup a postgre Multi-AZ DB cluster deployment (3 instances) and as per the documentation there's a restriction of using s3 extension 
"RDS for PostgreSQL Multi-AZ DB clusters don't support the following extensions: aws_s3 and pg_transport." 
(https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/multi-az-db-clusters-concepts.Limitations.html)

However I'm not able to add Lambda extension neighter. 
When I try to attach a role on the cluster it shows the following message
"Adding a role to DB cluster isn't supported for DB engine postgres"

Is there this limitation too that's not on documentation?
And is there any workaround to call a lambda ?

thank you

re:Post Agent · Answer

You are correct that there are limitations for Multi-AZ DB clusters in Amazon RDS for PostgreSQL, and your observation about the aws_s3 extension not being supported is accurate.

Regarding the Lambda extension, while it's not explicitly mentioned in the limitations for Multi-AZ DB clusters, the error message you're receiving suggests that attaching IAM roles to PostgreSQL DB clusters is not supported for this configuration. This limitation appears to extend beyond just the s3 and pg_transport extensions.

The inability to add roles to a PostgreSQL DB cluster, including those for Lambda integration, seems to be a broader restriction for Multi-AZ DB clusters. This limitation is likely due to the architecture of Multi-AZ DB clusters, which are designed for high availability across multiple Availability Zones.

It's important to note that these limitations are specific to Multi-AZ DB clusters. If you require functionality like Lambda integration or the aws_s3 extension, you might need to consider using a different RDS deployment option, such as a single-instance deployment or a Multi-AZ deployment with a standby replica (which is different from a Multi-AZ DB cluster).

If these features are critical for your use case, you may want to reach out to AWS support for further clarification or to explore alternative solutions that can meet your requirements while maintaining high availability.  
**Sources**  
[Limitations of Multi-AZ DB clusters for Amazon RDS - Amazon Relational Database Service](https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/multi-az-db-clusters-concepts.Limitations.html)  
[Creating a Multi-AZ DB cluster for Amazon RDS - Amazon Relational Database Service](https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/create-multi-az-db-cluster.html)

Jainam · Answer

I can confirm that attaching IAM roles to RDS PostgreSQL clusters is currently not supported. This is a known limitation of Multi-AZ DB clusters for PostgreSQL [1]. While this feature isn't available for PostgreSQL clusters, you can still attach IAM roles to individual RDS PostgreSQL instances [2]. If your use case allows, this could be an alternative solution.

As a workaround, you might want to consider: 
* Using individual RDS PostgreSQL instances instead of clusters if IAM role attachment is crucial for your use case

* Implementing alternative authentication methods that are currently supported for PostgreSQL clusters [3]

References:

[1] Multi-AZ DB cluster limitations - https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/multi-az-db-clusters-concepts.html#multi-az-db-clusters-concepts.Limitations

[2] Adding IAM roles to RDS PostgreSQL instances - https://repost.aws/knowledge-center/rds-postgresql-connect-using-iam

[3] Authentication methods for RDS PostgreSQL - https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Appendix.PostgreSQL.CommonDBATasks.html#Appendix.PostgreSQL.CommonDBATasks.Authentication

Aws RDS postgre multi-az db cluster - Failling add s3 lambda role

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