Looks like Nuxt/Vue sitting on S3 with CloudFront as CDN. Presumably with some script on the backend to update the list of Tweets on S3.

/vaguely informed guessing

Yup, It's one simple lambda function that reads the JSON file from S3, searches twitter for new tweets since the latest, appends new ones and writes back to S3. Cron'd every minute.

This is awesome! What is the strategy to identify the idea tweets? It looks like some string matching, but I'm not sure.

Yes, nothing too special. There are 6 or 7 string matches e.g. "I need an app that" (minus retweets). But also retrieving referenced tweets.