python or c# desktop app for comparing csv to master csv data

I have a master list of email addresses that we manage and I need to be able to compare a csv against that master list to see what the status is for each of the emails. I see the solution like this we have 2 csv files [login to view URL] - 3 columns of data (email, Status 1, Status 2) [login to view URL] - 1 column (email) each row in [login to view URL] will be looked up in master.csv. there are cases when an email will live more than 1 time in the master, in that case we get all of the matches for it, dedup, and concate to a single column. then for status 2 there are most cases where this empty I would like an exe or cli method where i run it and give it both sheets and then it outputs a [login to view URL] file will all of the lookup results. the output of that file should be email, found/not found, status 1, status 2 the master will need to be able to handle upwards of a million rows, the lookup csv will have 100-300K at its upper range. you can assume windows 10 machine, lots of cores if you want to parallel the task, and plenty of memory (20gb free ram is np) if you want to load both sets of data to some B-tree or binary tree in memory or something like that. when done we need some basic document on how the solution is structured and how to run it. I have put this sample together for you to see what we need. [login to view URL] it covers each output file needed, the issue with duplicates as well as the issue of not found.