I did end up setting up a staging server (was pretty easy to do, actually - just restored a backup from prod and logged in using the admin recovery procedure, since it’s configured for OIDC only). Looks like we have about 160K topics, and a quick test on just one category with about 7500 took 6 minutes on my test system - so about 2 hours for all topics. The impact on system performance (monitored with htop) seemed pretty negligible here.
I’m sure we can find a low usage time period where the rake command can be run, and we can stage groups of categories if we want, so that’ll work really nicely for us.
Appreciate all the tips and help - learned a lot about the platform over the last couple of days as a result. 