Which endpoints are you trying to call?
429 is the rate limit warning, and the rate limit is passed in the headers
You can use a App Access Token, which’ll grant a limit of 800 request per minute (client-id only is 30)
Additionally both the users and streams endpoints allow you to look up 100 users at once.
Then your front end should call your server and your server should load from a cache and your cache be updated via a Cron job.
So 10k people can load your website, but your website loads from the API once per minute total.
Every page load it loads from your database, and you have cronjob that updates every minute or so instead.
See also this thread
About upcoming changes, requiring an oAuth bearer to be present on all Helix requests. (Which’ll also grant the 800 rate limit)