Coffee chain Starbucks Corp said on Thursday it would buy the remaining 50% share of its East China business from its joint venture (JV) partners for about $1.3 billion, in its biggest ever acquisition. China is Starbucks’ fastest-growing market outside the United States by number of stores. The cash deal will give Starbucks ownership of about 1,300 stores in Shanghai and Jiangsu and Zhejiang provinces, and aligns with its target of operating 5,000 stores in mainland China by 2021. Shanghai has almost 600 Starbucks outlets, the largest number in any city. It will also be the first city outside the United States to have a coffee roastery and tasting room, set to open in December this year, Reuters reports. Starbucks is contending with a slowdown in in-store traffic back home as it works to speed up service at its cafes, where a large number of mobile orders had led to congestion and delays in serving orders.