← Netflix Interview Insights

Netflix·Software Engineer·Onsite - System Design / Architecture·Senior

Senior
Jun 2026

Summary

Netflix system design round focused on ad tech internals, specifically how the DSP side models and tracks an order. Pretty niche stuff if you haven't worked in programmatic advertising before.

Questions Asked (1)

Q1

Walk through how the DSP side of an ad platform tracks an order. Include all the relevant config types, and keep in mind the order is direct sold demand with no open auction involved.

Data ModelingSystem DesignTechnical Trade-offs
Author's notes

This one exposed how much my mental model was built around RTB and open auction flows.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the scope: direct sold demand means no real-time bidding, so the DSP focuses on guaranteed delivery and accurate tracking. Walk through the order lifecycle from ingestion to reporting, highlighting the config types (order, line item, creative, targeting) and how they map to tracking events. Emphasize data modeling choices and trade-offs for scalability and consistency.

Pro tip: Mention that direct sold deals often require reconciliation with the ad server and that idempotency and deduplication are critical to avoid overcounting impressions. Also, note that Netflix's ad tier likely uses a server-side ad insertion (SSAI) approach, so tracking must handle both client and server events.

1. Clarify scope and assumptions

Confirm that 'order' refers to a direct sold campaign with guaranteed impressions, and that tracking includes impression, click, and conversion events. State assumptions about the ad serving environment (e.g., SSAI, client-side).

2. Describe config types and hierarchy

Explain the config types: Order (advertiser, budget, flight dates), Line Item (targeting, priority, guaranteed impressions), Creative (assets, duration), and Targeting (audience, geo, content). Show how they relate in a hierarchy.

3. Walk through the tracking flow

Detail the steps: order ingestion, config validation, ad decisioning (matching line items to avails), ad delivery, and event tracking (impression, click, quartile). Highlight where tracking pixels or beacons are fired.

4. Discuss data modeling and storage

Describe how tracking events are modeled (e.g., fact tables for events, dimension tables for configs) and stored (e.g., Kafka for streaming, data lake for batch). Mention partitioning and indexing for query performance.

5. Address trade-offs and challenges

Talk about trade-offs: consistency vs. latency, exactly-once vs. at-least-once processing, and how to handle discrepancies between DSP and ad server counts. Mention reconciliation and idempotency.

Key Points to Mention

  • Direct sold demand means no real-time bidding; focus on guaranteed delivery and priority.
  • Config types: Order, Line Item, Creative, Targeting, and their relationships.
  • Tracking events: impression, click, quartile, and conversion, with server-side and client-side firing.
  • Data modeling: star schema with fact and dimension tables, or event sourcing for auditability.
  • Scalability: use of Kafka for event streaming, batch processing for aggregation, and partitioning by date/advertiser.
  • Trade-offs: latency vs. accuracy, idempotency, deduplication, and reconciliation with ad server logs.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.