how to ensure rtsp streams to eu-west-1 based KVS

You can change the target KVS region using the parameters at the end of the "gst-launch-1.0" command when you start streaming.
From the docs, https://docs.aws.amazon.com/kinesisvideostreams/latest/dg/examples-gstreamer-plugin.html this is the command for MacOS:

 $ gst-launch-1.0 rtspsrc location="rtsp://YourCameraRtspUrl" short-header=TRUE ! rtph264depay ! video/x-h264, format=avc,alignment=au ! kvssink stream-name="YourStreamName" storage-size=512  access-key="YourAccessKey" secret-key="YourSecretKey" aws-region="YourAWSRegion"

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