I don’t know about the capability of DSInternals, having never used it. I agree that a C# may well be quicker, but Python is what I mainly know so its what I stuck with. It does implement multiprocessing to speed things up, the more resources you have, the quicker it runs. I have been running it on an 80 core cloud instance and it checks around 7000 accounts against the 550 million HIBP hashes in around 45 minutes.
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