Learned D3 at Businessweek, started using Observable to do my job at Kensho, took time off to write notebooks about Mayans and Galton, moved to San Francisco to work for Observable. Now work for it remotely from the Berkshires where my wife runs Avaloch.
You might consider using a hash instead of a query string, since hashes are not sent to the server (and thus will not be logged). For example here in the client-side decryption here:
https://observablehq.com/@mbostock/encrypted-message