Please find the answers of your question.

1. Yes, this change only impacts inactive pipelines that have at least one source action configured to poll for changes. If you have an active pipeline, or if your inactive pipeline only uses Amazon EventBridge rule, AWS CodeStar Connections, or webhooks to trigger the pipeline, then it will not be affected by this change.
2. Yes, if an inactive pipeline is made active within the next 30 days before May 25, 2023 and has a pipeline execution started, then it will not be considered inactive and will not have its polling disabled. However, if the pipeline remains inactive for 30 days after the last pipeline execution, then its polling will be disabled.
3. The change is primarily driven by the need to improve performance for pipeline executions by ensuring they respond to source changes quicker. Polling is a resource-intensive operation that can impact the performance of the pipeline, especially when multiple pipelines are polling for changes on the same repository or source location. By moving to event-driven triggers, pipeline executions can be triggered more quickly and efficiently, without the need for polling. This can improve the overall performance of AWS resources and benefit both AWS and customers.

In the CDK you can add trigger in codepipeline_actions.S3SourceAction to resolve it.

P.S.: Do not forget setting CloudTrail for dataEvents [4] source: [1] https://github.com/aws/aws-cdk/blob/5bdb0128e8181cd3a33a118a1f121f67b0f78b20/packages/aws-cdk-lib/aws-codepipeline-actions/lib/s3/source-action.ts#LL135C76-L135C85 [2] https://docs.aws.amazon.com/codepipeline/latest/userguide/reference-pipeline-structure.html#action-requirements [3] https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_codepipeline_actions.S3SourceAction.html [4] Do not forget setting CloudTrail for dataEvents : https://docs.aws.amazon.com/AmazonCloudWatch/latest/events/log-s3-data-events.html

import * as cloudtrail from 'aws-cdk-lib/aws-cloudtrail';

declare const sourceBucket: s3.Bucket;
const sourceOutput = new codepipeline.Artifact();
const key = 'some/key.zip';
const trail = new cloudtrail.Trail(this, 'CloudTrail');
trail.addS3EventSelector([{
  bucket: sourceBucket,
  objectPrefix: key,
}], {
  readWriteType: cloudtrail.ReadWriteType.WRITE_ONLY,
});
const sourceAction = new codepipeline_actions.S3SourceAction({
  actionName: 'S3Source',
  bucketKey: key,
  bucket: sourceBucket,
  output: sourceOutput,
  trigger: codepipeline_actions.S3Trigger.EVENTS, // default: S3Trigger.POLL <----
});

I have doubts about this because I used the script to verify if my pipelines are polling pipelines and the script return that YES, but all my pipelines are using s3 as source and in the Change detection options Amazon cloudwatch events and the AWS support told me that this kind of pipelines won't be affected, so the script said yes but aws support said no