Design Video Collaboration - System Design | WinJob

Problem Statement and Video Collaboration Context

Problem framing

Frame.io, Vimeo Review, and Wipster let post-production teams leave timecoded feedback on video without exporting clips. The system is metadata-heavy, video-light: bytes live on CDN; we own threads, permissions, and notifications.

Design choices

Upload or link source video; reviewers comment at timestamps
Draw frame-accurate annotations overlaid on player
Threaded replies with @mentions and resolve workflow
Real-time presence: who is watching which frame
Version stack when editor uploads new cut

Deep dive

Walk the journey: producer shares review link → client scrubs to 01:14 → pins comment + arrow annotation → editor gets email + in-app badge → uploads v2 → system offers to copy unresolved threads by time offset.

javaOne Dark Pro

1 public final class TimecodedComment {
2   private final String assetVersionId;
3   private final long startMs;
4   private final long endMs;
5   private final String authorId;
6  
7   public TimecodedComment(String assetVersionId, long startMs, long endMs, String authorId) {
8     this.assetVersionId = assetVersionId;
9     this.startMs = startMs;
10     this.endMs = endMs;
11     this.authorId = authorId;
12   }
13  
14   public boolean overlapsPlayback(long playheadMs) {
15     return playheadMs >= startMs && playheadMs <= endMs;
16   }
17 }

pythonOne Dark Pro

1 from dataclasses import dataclass
2  
3 @dataclass(frozen=True)
4 class ReviewThread:
5     thread_id: str
6     asset_version_id: str
7     start_ms: int
8     end_ms: int
9     status: str
10  
11 def is_open(thread: ReviewThread) -> bool:
12     return thread.status in {"open", "needs_revision"}

typescriptOne Dark Pro

1 interface ReviewThread {
2   threadId: string;
3   assetVersionId: string;
4   startMs: number;
5   endMs: number;
6   status: "open" | "resolved" | "needs_revision";
7 }
8  
9 export function isOpen(thread: ReviewThread): boolean {
10   return thread.status === "open" || thread.status === "needs_revision";
11 }

Interviewer positioning

Assume 500K DAU across agencies; average asset 12 minutes ProRes proxy; 8 reviewers per project peak.

Appendix note 1: Draw frame-accurate annotations overlaid on player, frame-accurate anchors, asset_version_id, and review ACL for problem-statement.
Appendix note 2: Threaded replies with @mentions and resolve workflow, WebSocket presence, asset_version_id, and review ACL for problem-statement.
Appendix note 3: Real-time presence: who is watching which frame, annotation overlay JSON, asset_version_id, and review ACL for problem-statement.
Appendix note 4: Version stack when editor uploads new cut, version diff on re-upload, asset_version_id, and review ACL for problem-statement.
Appendix note 5: Upload or link source video; reviewers comment at timestamps, review workflow states, asset_version_id, and review ACL for problem-statement.
Appendix note 6: Draw frame-accurate annotations overlaid on player, signed media proxy, asset_version_id, and review ACL for problem-statement.
Appendix note 7: Threaded replies with @mentions and resolve workflow, comment fan-out, asset_version_id, and review ACL for problem-statement.
Appendix note 8: Real-time presence: who is watching which frame, optimistic UI merge, asset_version_id, and review ACL for problem-statement.
Appendix note 9: Version stack when editor uploads new cut, CRDT annotation sync, asset_version_id, and review ACL for problem-statement.
Appendix note 10: Upload or link source video; reviewers comment at timestamps, timecoded comments, asset_version_id, and review ACL for problem-statement.
Appendix note 11: Draw frame-accurate annotations overlaid on player, frame-accurate anchors, asset_version_id, and review ACL for problem-statement.
Appendix note 12: Threaded replies with @mentions and resolve workflow, WebSocket presence, asset_version_id, and review ACL for problem-statement.
Appendix note 13: Real-time presence: who is watching which frame, annotation overlay JSON, asset_version_id, and review ACL for problem-statement.
Appendix note 14: Version stack when editor uploads new cut, version diff on re-upload, asset_version_id, and review ACL for problem-statement.
Appendix note 15: Upload or link source video; reviewers comment at timestamps, review workflow states, asset_version_id, and review ACL for problem-statement.
Appendix note 16: Draw frame-accurate annotations overlaid on player, signed media proxy, asset_version_id, and review ACL for problem-statement.
Appendix note 17: Threaded replies with @mentions and resolve workflow, comment fan-out, asset_version_id, and review ACL for problem-statement.
Appendix note 18: Real-time presence: who is watching which frame, optimistic UI merge, asset_version_id, and review ACL for problem-statement.
Appendix note 19: Version stack when editor uploads new cut, CRDT annotation sync, asset_version_id, and review ACL for problem-statement.
Appendix note 20: Upload or link source video; reviewers comment at timestamps, timecoded comments, asset_version_id, and review ACL for problem-statement.
Appendix note 21: Draw frame-accurate annotations overlaid on player, frame-accurate anchors, asset_version_id, and review ACL for problem-statement.
Appendix note 22: Threaded replies with @mentions and resolve workflow, WebSocket presence, asset_version_id, and review ACL for problem-statement.
Appendix note 23: Real-time presence: who is watching which frame, annotation overlay JSON, asset_version_id, and review ACL for problem-statement.
Appendix note 24: Version stack when editor uploads new cut, version diff on re-upload, asset_version_id, and review ACL for problem-statement.
Appendix note 25: Upload or link source video; reviewers comment at timestamps, review workflow states, asset_version_id, and review ACL for problem-statement.
Appendix note 26: Draw frame-accurate annotations overlaid on player, signed media proxy, asset_version_id, and review ACL for problem-statement.
Appendix note 27: Threaded replies with @mentions and resolve workflow, comment fan-out, asset_version_id, and review ACL for problem-statement.
Appendix note 28: Real-time presence: who is watching which frame, optimistic UI merge, asset_version_id, and review ACL for problem-statement.
Appendix note 29: Version stack when editor uploads new cut, CRDT annotation sync, asset_version_id, and review ACL for problem-statement.
Appendix note 30: Upload or link source video; reviewers comment at timestamps, timecoded comments, asset_version_id, and review ACL for problem-statement.
Appendix note 31: Draw frame-accurate annotations overlaid on player, frame-accurate anchors, asset_version_id, and review ACL for problem-statement.
Appendix note 32: Threaded replies with @mentions and resolve workflow, WebSocket presence, asset_version_id, and review ACL for problem-statement.
Appendix note 33: Real-time presence: who is watching which frame, annotation overlay JSON, asset_version_id, and review ACL for problem-statement.
Appendix note 34: Version stack when editor uploads new cut, version diff on re-upload, asset_version_id, and review ACL for problem-statement.
Appendix note 35: Upload or link source video; reviewers comment at timestamps, review workflow states, asset_version_id, and review ACL for problem-statement.
Appendix note 36: Draw frame-accurate annotations overlaid on player, signed media proxy, asset_version_id, and review ACL for problem-statement.
Appendix note 37: Threaded replies with @mentions and resolve workflow, comment fan-out, asset_version_id, and review ACL for problem-statement.
Appendix note 38: Real-time presence: who is watching which frame, optimistic UI merge, asset_version_id, and review ACL for problem-statement.
Appendix note 39: Version stack when editor uploads new cut, CRDT annotation sync, asset_version_id, and review ACL for problem-statement.
Appendix note 40: Upload or link source video; reviewers comment at timestamps, timecoded comments, asset_version_id, and review ACL for problem-statement.
Appendix note 41: Draw frame-accurate annotations overlaid on player, frame-accurate anchors, asset_version_id, and review ACL for problem-statement.
Appendix note 42: Threaded replies with @mentions and resolve workflow, WebSocket presence, asset_version_id, and review ACL for problem-statement.
Appendix note 43: Real-time presence: who is watching which frame, annotation overlay JSON, asset_version_id, and review ACL for problem-statement.
Appendix note 44: Version stack when editor uploads new cut, version diff on re-upload, asset_version_id, and review ACL for problem-statement.
Appendix note 45: Upload or link source video; reviewers comment at timestamps, review workflow states, asset_version_id, and review ACL for problem-statement.
Appendix note 46: Draw frame-accurate annotations overlaid on player, signed media proxy, asset_version_id, and review ACL for problem-statement.
Appendix note 47: Threaded replies with @mentions and resolve workflow, comment fan-out, asset_version_id, and review ACL for problem-statement.
Appendix note 48: Real-time presence: who is watching which frame, optimistic UI merge, asset_version_id, and review ACL for problem-statement.
Appendix note 49: Version stack when editor uploads new cut, CRDT annotation sync, asset_version_id, and review ACL for problem-statement.
Appendix note 50: Upload or link source video; reviewers comment at timestamps, timecoded comments, asset_version_id, and review ACL for problem-statement.
Appendix note 51: Draw frame-accurate annotations overlaid on player, frame-accurate anchors, asset_version_id, and review ACL for problem-statement.
Appendix note 52: Threaded replies with @mentions and resolve workflow, WebSocket presence, asset_version_id, and review ACL for problem-statement.
Appendix note 53: Real-time presence: who is watching which frame, annotation overlay JSON, asset_version_id, and review ACL for problem-statement.
Appendix note 54: Version stack when editor uploads new cut, version diff on re-upload, asset_version_id, and review ACL for problem-statement.
Appendix note 55: Upload or link source video; reviewers comment at timestamps, review workflow states, asset_version_id, and review ACL for problem-statement.

Why interviewers care

Video Collaboration interviews reward crisp scope, explicit trade-offs, and failure stories—not generic microservice diagrams.

Interview checkpoint

Name one failure story for Problem Statement and Video Collaboration Context that proves you understand real outages, not happy-path diagrams.

Key Highlights

•Upload or link source video; reviewers comment at timestamps
•Draw frame-accurate annotations overlaid on player
•Threaded replies with @mentions and resolve workflow

1	public final class TimecodedComment {
2	private final String assetVersionId;
3	private final long startMs;
4	private final long endMs;
5	private final String authorId;
6
7	public TimecodedComment(String assetVersionId, long startMs, long endMs, String authorId) {
8	this.assetVersionId = assetVersionId;
9	this.startMs = startMs;
10	this.endMs = endMs;
11	this.authorId = authorId;
12	}
13
14	public boolean overlapsPlayback(long playheadMs) {
15	return playheadMs >= startMs && playheadMs <= endMs;
16	}
17	}

1	from dataclasses import dataclass
2
3	@dataclass(frozen=True)
4	class ReviewThread:
5	thread_id: str
6	asset_version_id: str
7	start_ms: int
8	end_ms: int
9	status: str
10
11	def is_open(thread: ReviewThread) -> bool:
12	return thread.status in {"open", "needs_revision"}

1	interface ReviewThread {
2	threadId: string;
3	assetVersionId: string;
4	startMs: number;
5	endMs: number;
6	status: "open" \| "resolved" \| "needs_revision";
7	}
8
9	export function isOpen(thread: ReviewThread): boolean {
10	return thread.status === "open" \|\| thread.status === "needs_revision";
11	}