# Chapter 9 Lab Exercises

## Exercise 1: Compare lateness policies

Run the simulator twice, once with `--allowed-lateness-seconds 20` and once with `--allowed-lateness-seconds 0`. Compare the metrics and late-event files. Explain which windows changed and why.

## Exercise 2: Add an operational signal

Extend `streaming_window_simulator.py` to print a warning when the late-event count is greater than zero. In a real system, this warning would become a dashboard metric or alert.

## Exercise 3: Design a replay procedure

Write a short runbook that explains how you would replay the raw topic into a new output version after changing the lateness policy from 0 seconds to 20 seconds. Include the input topic, checkpoint policy, output version, and validation checks.