Project Reactor · interview question

In a Project Reactor pipeline, why would you use flatMap() instead of map() to handle a stream of product IDs that need to be fetched from a remote service?

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FlatMap() is more efficient for synchronous operations.Map() cannot transform data into different reactive types.FlatMap() allows asynchronous fetching of data, enabling concurrent I/O operations.Map() is only for transforming data types, not fetching remote data.

Answer and explanation

Correct answer

C. FlatMap() allows asynchronous fetching of data, enabling concurrent I/O operations.

Why

flatMap() is used to handle asynchronous operations because it can take each input element and return a publisher, enabling non-blocking I/O operations. Unlike map(), which transforms data synchronously, flatMap() allows for concurrent fetching and processing of data, making it suitable for remote service calls.

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In a Project Reactor pipeline, why would you use flatMap() instead of map() to handle a stream of product IDs that need to be fetched from a remote service?

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