Refactor expire_windows - simplify code

quixstreams/state/rocksdb/windowed/transaction.py

@@ -183,34 +183,24 @@ def expire_windows(
             Relevant only together with `collect=True`.
         :return: A sorted list of tuples in the format `((start, end), value)`.
         """
-        start_from = -1
+        cache = self._last_expired_timestamps
 
         # Find the latest start timestamp of the expired windows for the given key
-        last_expired = self._get_timestamp(
-            cache=self._last_expired_timestamps, prefix=prefix
-        )
-        if last_expired is not None:
-            start_from = max(start_from, last_expired)
+        start_from_ms = self._get_timestamp(cache=cache, prefix=prefix) or -1
 
         # Use the latest expired timestamp to limit the iteration over
         # only those windows that have not been expired before
         expired_windows = self.get_windows(
-            start_from_ms=start_from,
+            start_from_ms=start_from_ms,
             start_to_ms=max_start_time,
             prefix=prefix,
         )
         if not expired_windows:
             return []
 
         # Save the start of the latest expired window to the expiration index
-        latest_window = expired_windows[-1]
-        last_expired__gt = latest_window[0][0]
-
-        self._set_timestamp(
-            cache=self._last_expired_timestamps,
-            prefix=prefix,
-            timestamp_ms=last_expired__gt,
-        )
+        timestamp_ms = expired_windows[-1][0][0]  # [..., [(start, end), value]]
+        self._set_timestamp(cache=cache, prefix=prefix, timestamp_ms=timestamp_ms)
 
         if not collect:
             return expired_windows