That's almost certainly per server instance though, there's no mention of any type of synchronization across multiple instances, so if you e.g run many small ones or run the service as a lambda I'd be surprised if it worked like you expected.
IMO Lambda is kind of an unfair example because the author doesn't mention having multiple instances. Plus a hot take I have is you should not be building an entire web-app as a Lambda or series of Lambda functions... AWS does not have solutions for load balancing in things like APIG so you would have to architect that via DynamoDB or ElastiCache which is the "extra layer or two of overhead" the author mentioned.
