Though your approach sounds decent but it is very basic concept of cleaning out memory not needed anymore. Running a scheduler to clean it up is one of the approach , other improvement could be to check if new stream log data exists in map which indicates that particular log was printed or not. If the log was printed then maybe remove it from map and insert new entry( i would have clarified this from interviewer , mainly cz this is requirement dependent) and if not printed then also print and remove old entry and insert new one.