[Screenshot from 2022-11-28 19-00-07] _id 1,2,3 have already existed, we can insert document with _id 4 and 5, why is it incorrect ?

Hi :wave: @Tuan_Anh_Le , Welcome to the MongoDB Community forums :sparkles: [image] Tuan_Anh_Le: What are the correct answers for connection pooling advantages ? [CP] The above screenshot shows that your selected answer is marked with black, which indicates that one of the options selected…