According to their SEC fillings their staff almost tripled in just 4 years
> Dec 31, 2022 7,703
> Dec 31, 2021 5,245
> Dec 31, 2020 4,001
> Dec 31, 2019 2,715
Development of game engine is costly and take a lot of resources, but they already had a successful product back in 2019 and long before that. With all that hiring quality of their software was more or less constant (and not too high as always) which means all recent growth was not in their core business.