I was part of McKinsey Southeast Asia office, 20% of my projects were placed in Vietnam. In fact, in late 2018 when I had a project in Hanoi, I was also helping recruitment for Consulting Analyst from CFP program (consulting fellowship program).
There are 2 offices in Vietnam: at Hanoi and Ho Chi Minh. Hanoi office is bigger and has more consultants than HCM, but they are still very small compared to other SEA offices. In 2018, I think it was less than 30 consultants from Hanoi office and less than 20 consultants from HCM. Given the size, they are very close to each other, and as the incoming consultant, we were often invited to their internal events.
PM me if you need further info or have more questions.