Technically, Discourse, and most softwares would be able to scale up to a point you don’t really need to worry about.
Discourse powering forums like Gitlab’s, Let’s Encrypt’s, Mozilla’s this is in no way an issue. If you know you will have a lot of traffic go for a separated database and data deployment, if the traffic won’t be huge, but you’ll have a lot of users using the platform intermittently, you just need to keep an eye in the response times and increase the server size.