Is it necessary to restart unicorn, sidekiq, and/or redis for the changed value to take effect? I turned rebake_old_posts_count down to 1 to try to clear sidekiq but the enqueued count is going up, not down, so it’s not clear that the setting is being honored. Or is there some other reason for over 14K Jobs::CrawlTopicLink jobs enqueued, and growing? I don’t know whether that’s the right job for that setting. 
I made this change because we’re seeing something that looks superficially like this on forum.makerforums.info (hosted on DO) after importing about 37.5K topics with about 260K total posts, many of which are image-heavy with a total of about 33GB images. We had CDN configured and functional before the import; it looks like making the posts at import time didn’t use the CDN configuration and maybe is slowly re-baking to point at the CDN? The reprocessing is definitely taking much longer than the initial import, which really surprised me.
Update: It took over 12 hours to recover, but the sidekiq queue has cleared.