Retailers were already facing rapid change before Covid-19 struck. But the pandemic prompted a surge in e-commerce that is overwhelming retail supply chains. Between March and September 2020, US online orders at Walmart more than tripled to 20% of sales; at Best Buy, they more than doubled to 50%. At the same time, digital pioneers like Amazon have raised customer expectations on speed of delivery to one day or less. And the biggest challenge is yet to come: Bain & Company research shows that US retail e-commerce penetration will grow to nearly 30% of total sales by 2025.