Could you tell us a little more about your use case and setup? A lambda function running on a Greengrass Core device can be made on-demand which runs when it receives work items and Greengrass runs multiple instances for it if there are more work items to be processed simultaneously. If your scale can be easily managed by the hardware for your IoT edge server(Greengrass Core), this will be may be sufficient for you. https://docs.aws.amazon.com/greengrass/v2/developerguide/import-lambda-function-console.html
Greengrass also provides the aws.greengrass.StreamManager component for data streaming use cases which you can use to stream data to cloud https://docs.aws.amazon.com/greengrass/v2/developerguide/stream-manager-component.html.
Scaling lambda function horizontally in cloud when a single Greengrass Core device cannot handle the workload is not supported natively, but you may be able to route data/messages from the Greengrass device to cloud lambda function on your own or setup multiple Greengrass Cores on the edge to handle high workload.
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