Code Room
CodingMediumcod-g686
Subject Stream processingLevel Mid–Senior~30 minCommon in Distributed systems interviewsIndustries Software development, Technology

Question

Deduplicate a stream within a time window. You are given events as [timestamp, key] in non-decreasing timestamp order. An event is a duplicate (and should be dropped) if an event with the SAME key was already EMITTED with a timestamp within the last `window` seconds (i.e. emitted_ts > timestamp - window). Otherwise the event is emitted and becomes the new reference for that key. Return the list of emitted keys in order.

Implement
dedup_window(events: list[list], window: int) → list
Examples
in[[[0,"a"],[1,"a"],[10,"a"]],5]out["a","a"]
What a strong answer looks like

State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.

Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.

Run or narrate your approach, then ask the coach.