By "process" I mean: Read the headline and sometimes the summary, decide whether to read the story, open the story (if I'm reading it), delete the feed item. Repeat 1,000x.
Deduplication is necessary but will only cut items process by maybe 5%, I would guess.
'Grouping' is much more valuable - grouping feed items by topic. For example, after the big event last night, instead of skimming dozens of headlines interspersed among 1,000 others, group together the feed items for that event under a single headers. Then I can quickly pick out the item I want to read and discard the remainder en masse. I'd guess that it would reduce the feed items I need to process by well over 50%.
Other tricks are needed too: 1,000 in 20 minutes is just under 1 feed item per second.