Learning Concurrency in Kotlin

Use case – streaming data

Recently, I was faced with a relatively simple programming task: querying 10 content indexers for a specific keyword, and then displaying the results of the search to the user. A valid first approach would have been to launch a coroutine for each content indexer, returning Deferred<List<ResultDto>>, and upon completion of all of the coroutines, merging the results and sending them to the UI.

A representation of this approach could look like this:

In this example, search() starts three coroutines, giving them the keywords to search. Each coroutine will fetch the results from the indexer. Upon completion of the three ...