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 medium 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.

Build and optimize a video playlist component

Quick Overview

Build and optimize a video playlist component evaluates requirements, scale assumptions, API/data design, architecture, trade-offs, failure modes, and rollout in a realistic interview setting. A strong answer states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.

Build and optimize a video playlist component

Design and implement a video playlist component in React (functional components) that meets the following requirements:

Display a list or grid of video thumbnails.
When a thumbnail is clicked, start playing that video and ensure all other videos stop — only one video plays at a time.
Provide a "Play All" control that automatically plays all videos sequentially and stops at the end.

Outline your approach and key decisions (state with hooks, refs to player elements, effect handling, media event listeners). Then address the following follow-ups:

How would you optimize performance when the list contains many videos (e.g. virtualization, lazy loading, thumbnail vs. player mounting, memoization, preload strategy)?
How would you structure state management for clarity and scalability (lifting state, React Context, reducer patterns, controlled vs. uncontrolled items)?
How would you split the component hierarchy and define props/interfaces to improve maintainability and extensibility (e.g. Playlist, VideoItem, Controls)?
What accessibility and browser autoplay considerations would you address?

Constraints & Assumptions

Preserve the scope, facts, inputs, and requested outputs from the prompt above.
If the prompt leaves a detail unspecified, state a reasonable assumption before relying on it.
Keep the answer interview-ready: concise enough to present, but concrete enough to implement or evaluate.

Clarifying Questions to Ask Guidance

Clarify users, core use cases, read/write patterns, scale, latency, availability, and data retention.
State explicit assumptions before making sizing or architecture decisions.
Prioritize the functional path first, then address reliability, security, observability, and rollout.

What a Strong Answer Covers Guidance

A scoped requirements summary with concrete non-goals and success metrics.
API, data model, architecture, consistency, capacity, and operations.
Reasoned trade-offs among simple and scalable designs, including bottlenecks and failure modes.
A validation, monitoring, migration, and launch plan appropriate for the risk level.

Follow-up Questions Guidance

What breaks first at 10x traffic or data volume?
How would you degrade gracefully during dependency failures?
What metrics and alerts would prove the design is healthy after launch?

Quick Overview

Build and optimize a video playlist component

Design and implement a video playlist component in React (functional components) that meets the following requirements:

Display a list or grid of video thumbnails.

When a thumbnail is clicked, start playing that video and ensure all other videos stop — only one video plays at a time.

Provide a "Play All" control that automatically plays all videos sequentially and stops at the end.

Outline your approach and key decisions (state with hooks, refs to player elements, effect handling, media event listeners). Then address the following follow-ups:

How would you optimize performance when the list contains many videos (e.g. virtualization, lazy loading, thumbnail vs. player mounting, memoization, preload strategy)?

How would you structure state management for clarity and scalability (lifting state, React Context, reducer patterns, controlled vs. uncontrolled items)?

How would you split the component hierarchy and define props/interfaces to improve maintainability and extensibility (e.g. Playlist, VideoItem, Controls)?

What accessibility and browser autoplay considerations would you address?

Constraints & Assumptions

Preserve the scope, facts, inputs, and requested outputs from the prompt above.

If the prompt leaves a detail unspecified, state a reasonable assumption before relying on it.

Keep the answer interview-ready: concise enough to present, but concrete enough to implement or evaluate.

Clarifying Questions to Ask Guidance

Clarify users, core use cases, read/write patterns, scale, latency, availability, and data retention.

State explicit assumptions before making sizing or architecture decisions.

Prioritize the functional path first, then address reliability, security, observability, and rollout.

What a Strong Answer Covers Guidance

A scoped requirements summary with concrete non-goals and success metrics.

API, data model, architecture, consistency, capacity, and operations.

Reasoned trade-offs among simple and scalable designs, including bottlenecks and failure modes.

A validation, monitoring, migration, and launch plan appropriate for the risk level.

Follow-up Questions Guidance

What breaks first at 10x traffic or data volume?

How would you degrade gracefully during dependency failures?

What metrics and alerts would prove the design is healthy after launch?

Build and optimize a video playlist component

Quick Overview

Build and optimize a video playlist component

Build and optimize a video playlist component

Constraints & Assumptions

Clarifying Questions to Ask Guidance

What a Strong Answer Covers Guidance

Follow-up Questions Guidance

Submit Your Answer to Earn 20XP

Build and optimize a video playlist component

Quick Overview

Build and optimize a video playlist component

Build and optimize a video playlist component

Constraints & Assumptions

Clarifying Questions to Ask Guidance

What a Strong Answer Covers Guidance

Follow-up Questions Guidance

Submit Your Answer to Earn 20XP