I'm always fascinated by these decisions. Having only worked at smaller companies, I've never been involved in moving an entire stack away from the current/primary language. The feature backlog coming from the business never, ever, includes items like "change programming languages". It's always filled with customer or business facing features. And when faced with tough deadlines, as the adage goes, the devil you know is better than the devil you don't.<p>I have worked on some legacy systems with languages like classic ASP and ColdFusion, and I would advocate against continuing to use them, only to ultimately be met with some feature request deadline. I know Roblox employs a ton of engineers (alright, more than a ton) but this decision couldn't have come lightly. How did this change come to be? Seems like it was a slow, organic, port of parts of their system over to Lua. What percentage of their engineering resources was spent working on this port, and will the gains made from switching to Lua outweigh the loss of productivity on the feature request backlog? Maybe they were blocked by JS and could only solve certain problems with Lua? Either way, this is very neat and makes me wonder what effect this will have on the job market, and if more large organizations going to follow suit and abandon JS in favor of Lua...