Jonathan Um, Cofounder, and COO of Holler.com, the world's first online dollar store recently spoke at Retail (R)Evolution 2018 about how important the supply chain and automation is to his young start-up. Jonathan Um, Cofounder, and COO of Holler.com, the world's first online dollar store recently spoke at Retail (R)Evolution 2018 about how important the supply chain and automation is to his young start-up.