S3 Batch Operations + Lambda to bulk rename objects

You could also consider adding a JSON structure like this in your manifest, which would eliminate the need to store the new keys elsewhere:
{"origKey": "object1key", "newKey": "newObject1Key"}

You could put that in the manifest like this:
bucket,{"origKey": "object1key", "newKey": "newObject1Key"}
bucket,{"origKey": "object2key", "newKey": "newObject2Key"}
bucket,{"origKey": "object3key", "newKey": "newObject3Key"}

We would then send that JSON to the Lambda function as the S3 key and it can be parsed there to identify the original and the key key for each copy. Please note that the JSON would need to be URL encoded for this to work and each "key" entry would need to be less than 1024 characters

The URL encoded values you would actually use:

bucket,%7B%22origKey%22%3A%20%22object1key%22%2C%20%22newKey%22%3A%20%22newObject1Key%22%7D
bucket,%7B%22origKey%22%3A%20%22object2key%22%2C%20%22newKey%22%3A%20%22newObject2Key%22%7D
bucket,%7B%22origKey%22%3A%20%22object3key%22%2C%20%22newKey%22%3A%20%22newObject3Key%22%7D

Thank you rob for your guidance! I will attemp to implement this approach using the JSON structure in the CSV manifest. It looks like the perfect solution for my particular bulk rename case.