E-commerce retailers like Amazon face the challenge to assemble large numbers of picking orders each consisting of just a few order lines with low order quantities under great time pressure. Traditional picker-to-parts systems where human pickers retrieve order after order from stationary shelves are often ill-suited for these requirements, and today’s warehouses have evolved to technology-enriched logistics facilities that play a key role in retail supply chains. This talk given an overview on the alternative setups of modern e-commerce warehouses, elaborates on important optimization problems, and outlines future research challenges.