All API endpoints use caching, so you shouldn’t request the same data more than once per minute (as you could actually get erroneous data if you poll too fast as you could hit different cache servers with different data).
The fastest way would be to use the channel.update EventSub subscription type EventSub Subscription Types | Twitch Developers as this will send your server a notification of topic changes (there will still be some delay to this, but it will be the fastest option available).