Fastest I've scaled a large team was from 6 to over 130 in just about 1 year. Fastest I've had to down size was ~14 to 2 in 2 weeks.
I've scaled many other teams between those ranges and timeframes over the years. Like going from 1 to 20 in just over a month, that was crazy. Adding 20 people when you are already 200 people isn't nearly as hard as adding 20 when you are starting at 1.
Really depends on type of people and job functions you are hiring IMO. My large team scaling was ~98% engineers, which in general is far harder to do quickly than many others I have done. Knowledge workers are harder to find, recruit and retain than others just because in general they are independent thinkers and so mission is just as important as getting paid & benefits (at least it has been, but I see some changes lately). When hiring retail, manufacturing, factory type labor it is almost always pay/benefits which act as the major hurdle, but in general that is easier to overcome than selling many people on the company, goals and mission.
Downsizing is "easy" to do overall, but hard to do quickly & correctly.