Tweets are stored in MongoDB, number of tokens is calculated based on engagement tweet gets and total tweets that received tokens (more tweets = less tokens per enagagement score)

You can see code here:
https://github.com/fbslo/posh-bot-2/blob/master/scripts/calculateEngagementScore.js
https://github.com/fbslo/posh-bot-2/blob/master/scripts/calculateTokens.js