:wave: In Kotlin, we have `MutableSharedFlow`. It contains a buffer. How does it work internally? Is...

# coroutines

[hawklike]

👋 In Kotlin, we have MutableSharedFlow. It contains a buffer. How does it work internally? Is an emitted value removed from the buffer if all subscribers read the value?

[Sam]

Not necessarily—some of the buffer can form the replay cache, which is kept indefinitely and replayed to new subscribers. The docs here should help: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.flow/-shared-flow/

[hawklike]

Sorry, I oversimplified the question. The last emitted values are kept in the replay cache, but in the extra buffer, they are kept until all subscribers read them, right?

[Sam]

If there's no replay cache, a value in the buffer disappears once all subscribers have seen it, yes. (In that scenario, if there are no subscribers, values are dropped immediately and not buffered.) But if there's a replay cache, values in the extra buffer will eventually just make their way into that replay cache, as older values are consumed.

[hawklike]

Thank you for the great explanation.