Your filter isn't actually producing any benefit if the resulting collection isn't saved for further processing.

dataMapStorage.keys
  .foreach { key =>
    val value = dataMapStorage.get(key)
    if (currentTime.getMillis - value.getMillis > timeout) {
      // ... do some work with "value"
      dataMapStorage.remove(key)
    }
  }

Also, if dataMapStorage is just a key->value Map then couldn't you simplify it?

dataMapStorage.foreach { case (key, value) =>
    if (currentTime.getMillis - value.getMillis > timeout) {
      // ... do some work with "value"
      dataMapStorage.remove(key)
    }
  }

You could use collect() here but since the procedure results in a side-effect I think foreach() is more explanatory.

Your filter isn't actually producing any benefit if the resulting collection isn't saved for further processing.

dataMapStorage.keys
  .foreach { key =>
    val value = dataMapStorage.get(key)
    if (currentTime.getMillis - value.getMillis > timeout) {
      // ... do some work with "value"
      dataMapStorage.remove(key)
    }
  }

Also, if dataMapStorage is just a key->value Map then couldn't you simplify it?

dataMapStorage.foreach { case (key, value) =>
    if (currentTime.getMillis - value.getMillis > timeout) {
      // ... do some work with "value"
      dataMapStorage.remove(key)
    }
  }

You could use collect() here but since the procedure results in a side-effect I think foreach() is more explanatory.

Of course the real Scala FP approach is to avoid mutable data structures.

val newDataMapStorage = oldDataMapStorage.filter { case (key, value) =>
    if (currentTime.getMillis - value.getMillis > timeout) {
      // ... do some work with "value"
      false
    } else true
  }

Your filter isn't actually producing any benefit if the resulting collection isn't saved for further processing.

dataMapStorage.keys
  .foreach { key =>
    val value = dataMapStorage.get(key)
    if (currentTime.getMillis - value.getMillis > timeout) {
      // ... do some work with "value"
      dataMapStorage.remove(key)
    }
  }

Your filter isn't actually producing any benefit if the resulting collection isn't saved for further processing.

dataMapStorage.keys
  .foreach { key =>
    val value = dataMapStorage.get(key)
    if (currentTime.getMillis - value.getMillis > timeout) {
      // ... do some work with "value"
      dataMapStorage.remove(key)
    }
  }

Also, if dataMapStorage is just a key->value Map then couldn't you simplify it?

dataMapStorage.foreach { case (key, value) =>
    if (currentTime.getMillis - value.getMillis > timeout) {
      // ... do some work with "value"
      dataMapStorage.remove(key)
    }
  }

You could use collect() here but since the procedure results in a side-effect I think foreach() is more explanatory.