So I'm thinking of writers that are primarily known for their short stories so I can casually read 3 or 4 of their works a week while reading longer works at the same time. So far I've thought of Chekhov, Poe, Maupassant, and Carver, and I already have some Kafka on my Kindle. Anyone else I should look into?
Not "primarily known" for them, but after his main novel-writing period, Melville wrote short stories for magazines for a long time, there are some great ones, the best no doubt being "Bartleby the scrivener".
How has nobody mentioned Joyce yet?
You should also get Sherwood Anderson's Winesburg, Ohio. The chapters are all interrelated, and it reads almost like an ordinary novel, but each chapter can stand alone as it's own short story as well.
O. Henry. He has some masterful stories. The Gift of the Magi, of course. Also The Last Leaf, A Municipal Report, While the Auto Waits, and Springtime á la Carte, among others.
Vonnegut has some great quick reads. Besides his actual short stories and the fact that most, if not all, of his novels could easily be read in a day or two, I would also recommend God Bless You, Dr. Kevorkian as well as Happy Birthday, Wanda June.
F. Scott Fitzgerald is also more known for his novels, but during his life his main success were his short stories, which constituted the biggest part of his literary output. The Curious Case of Benjamin Button is one of those short stories.