Hey, all, if I have a Flink app that has a long sliding window of 1 month to calculate some metrics over the past month, when deploying it, does it mean that for the 1st month there will be no output? or how will Flink work in this case? Thank you!

It depends on your datasource and time semantics. If you are using event time and reading from head/latest, then yes it will take 1 month. If you set offsets to 1+ month back it would output results once the backlog has processed 1+ month of data. If you are using processing time, then again it would take 1 month.

suppose we are joining two streams with 1 month sliding windows, but both streams have unique keys. so technically as soon as matching keys are seen on both streams, flink can output the result. Does flink still wait 1 month before outputing the result?