@Ken Miller Transaction bundles are supported if you use SQL as the backend in Open Source FHIR Server.
If you are using Cosmos DB as backend, only batch bundles are supported right now.
If you need to check the outcome of the batch, you could look at the tests in our repo here
Also, please check if FhirLoader is an option for you.
As per the contributor of the repo, you should be able to load 700k resources in 30 minutes at 10000RU's
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