How do I approach System Design interview questions?

System Design questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master system design interviews.

What difficulty level is this interview question?

This is a hard difficulty System Design question, commonly asked during Technical Screen rounds at Netflix.

What role is this question designed for?

This question is commonly asked for Software Engineer candidates at Netflix during technical interviews.

Design viewport dedup for Netflix home page | Netflix Interview Question

Quick Overview

This question evaluates system-design and algorithmic competencies related to personalized content selection, deduplication, constraint enforcement (editorial pins, maturity/region), data modeling, latency budgeting, caching, progressive loading, conflict resolution/backfill, and experiment-driven measurement for an initial streaming-service viewport. It is commonly asked to assess an engineer's ability to balance architectural trade-offs between server- and client-side rendering while maximizing relevance under multiple constraints; the domain is System Design and the level of abstraction spans both high-level conceptual reasoning and practical application-level design details.

Design the Above-the-Fold Deduplicated Home Page Rendering

Context

You are designing the initial viewport ("above the fold") of a streaming service home page (e.g., Netflix). The first screen should show several horizontal rows of cells. Each cell displays a unique title. No duplicates are allowed within a row or across rows in the first screen.

Requirements

Deduplicate titles across all cells in the first screen and within each row.
Respect row themes, editorial pins, maturity/region constraints, and personalization.
Maximize user relevance/engagement for the first screen.
Provide an algorithm for selection/placement with conflict resolution and backfill.
Define a latency budget and discuss client-side vs server-side rendering.
Describe data modeling for rows and candidate items, personalization inputs, and constraints.
Explain handling of partial data, caching, progressive loading (as the user scrolls), and impact measurement.

Assumptions (for concreteness)

Initial viewport shows R rows, each with K_r visible cells (e.g., 3 rows × 6 cells on desktop; 2 × 3 on mobile).
You have per-user, per-row candidate lists with relevance scores available at request time.
Editorial pins can lock specific items into fixed positions.

Deliverables

Data model for rows and candidate items, including personalization inputs and constraints.
Algorithm to select and place items that maximizes relevance subject to deduplication and constraints, with conflict resolution and backfill.
Latency budget and deployment approach (client vs server).
Handling of partial data, caching strategy, and incremental loading as the user scrolls.
Experimentation plan and success metrics.

Quick Overview

Requirements

Deduplicate titles across all cells in the first screen and within each row.

Respect row themes, editorial pins, maturity/region constraints, and personalization.

Maximize user relevance/engagement for the first screen.

Provide an algorithm for selection/placement with conflict resolution and backfill.

Define a latency budget and discuss client-side vs server-side rendering.

Describe data modeling for rows and candidate items, personalization inputs, and constraints.

Explain handling of partial data, caching, progressive loading (as the user scrolls), and impact measurement.

Deliverables

Data model for rows and candidate items, including personalization inputs and constraints.

Algorithm to select and place items that maximizes relevance subject to deduplication and constraints, with conflict resolution and backfill.

Latency budget and deployment approach (client vs server).

Handling of partial data, caching strategy, and incremental loading as the user scrolls.

Experimentation plan and success metrics.

Design viewport dedup for Netflix home page

Quick Overview

Design the Above-the-Fold Deduplicated Home Page Rendering

Context

Requirements

Assumptions (for concreteness)

Deliverables

Solution

Submit Your Answer

Design viewport dedup for Netflix home page

Quick Overview

Design the Above-the-Fold Deduplicated Home Page Rendering

Context

Requirements

Assumptions (for concreteness)

Deliverables

Solution

Submit Your Answer