Every technical round.
One place to prep for it.

1def credit_tracker(events):
2    # Track allocations and client accounts
3    credits = {}
4    for ev in events:
5        if ev["type"] == "allocate":
6            credits[ev["client"]] = credits.get(ev["client"], 0) + ev["amount"]
7        elif ev["type"] == "consume":
8            current = credits.get(ev["client"], 0)
9            if current >= ev["amount"]:
10                credits[ev["client"]] = current - ev["amount"]
11    return credits