I've built an API that delivers live data all at once when a user submits a search for content. I'd like to take this API to the next level by delivering the API content to a user as the content is received instead of waiting for all of the data to be received before displaying. 
How does one go about this?
I think the better way to apply it is setting limit in your query. For example, If you have 1000 of records in your database, then retrieving all data at once takes time. So, if a user search a word 'apple', you initially send the database request with limit 10. And, you can set pagination or scroll feature at your front-end. If the user click next page or scroll your page, you can again send the database request with another limit 10 so that the database read action will not take more time to read the limited data.
Building an API