There's no Aldi or Ole in Beijing.
We do have Wumart, and Beijing/Hebei-specific Jingkelong.
Meituan also has its own virtual grocery store that you can order from and get delivery from. Many others (including Wumart through its Dmall portal) also have their own grocery delivery services.
Costco's reach is still quite limited, with only 5 locations in SH, Jiangsu, Zhejiang.