kayn uses Colorfulstan's RiotRateLimiter-node under the hood, but not exactly. I've created a minor fork which does not deviate from the main library in any significant way. It allows me to add features that I think would be useful for kayn, such as POST functionality for the tournament endpoints.
Rate limiting functionality is thus the same as in RiotRateLimiter-node. kayn is simply a high-level library that uses the rate limiter under the hood.
Head back to the README for configuring rate limiting functionality.