well, here is a hint: make it simple but significant

kiss.py

intervall = 60
unique_ids = {}
last_flush = 0
for msg in stream:
 unique_ids[msg["uid"]] = True #KISS
 if (msg["ts"] - intervall > last_flush):
   uniques = len( unique_ids.keys()) #ouch... but works
   print( "\t".join( ( msg["ts"], uniques ) ))
   last_flush = msg["ts"]
   unique_ids = {}