What's the upload volume - hours of video per day? Average video length?

1B DAU. 500 hours of video uploaded per minute (YouTube-scale). 100B watch events per day. Average video length 10 minutes; long-tail extends to 12-hour streams. Storage: exabyte-scale corpus.

What's the latency budget for live - 30 seconds is acceptable, sub-second (low-latency live) is much harder?

Time-to-first-frame p99 < 2 seconds (the user pressed play; they're waiting). Adaptive bitrate decisions in <1 second. Live latency: 5-30 seconds is standard; <2 seconds is 'low-latency' tier (much harder).

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Streaming

Design a Video Streaming Service (YouTube / Netflix)

Hard Premium

Encoding ladders, adaptive bitrate, CDN economics, and the difference between live and VOD. Petabyte-scale storage meets millisecond-scale playback.

The problem

Design a service that lets users upload video, stores it durably, transcodes it into multiple qualities, and streams it to viewers globally with sub-second startup and adaptive quality. Variants: VOD (video on demand, like YouTube/Netflix), live streaming (Twitch/YouTube Live), or both.

Video is one of the highest-bandwidth, highest-cost design questions. The interesting decisions are: how to transcode efficiently, how the encoding ladder is structured, how the CDN absorbs petabit-scale traffic, and the operational cost of every choice.

Clarifying questions

Asking these before diving into a solution is the difference between a "hire" and a "no signal" rating. Pick the questions whose answers would change your design.

→Are we designing VOD, live, or both? They share storage but diverge sharply on the playback path.
→What's the upload volume - hours of video per day? Average video length?
→How many concurrent viewers at peak - 1M? 100M? The CDN strategy depends sharply.
→What qualities do we serve - SD, HD, 4K? Mobile-only?
→Are we serving global users (CDN strategy is critical) or single-region?
→What's the latency budget for live - 30 seconds is acceptable, sub-second (low-latency live) is much harder?
→Do we need DRM, watermarking, geo-blocking?
→Monetization model - ads (which inject mid-stream), subscription, free?

Requirements

Functional requirements

·Upload video file or live stream
·Transcode into multiple qualities (encoding ladder)
·Generate streaming manifest (HLS or DASH)
·Stream video to client with adaptive bitrate
·Generate thumbnails, previews, scrub-bar art
·Serve via global CDN with low first-byte latency
·Track watch progress, recommendations input

Non-functional requirements

Scale: 1B DAU. 500 hours of video uploaded per minute (YouTube-scale). 100B watch events per day. Average video length 10 minutes; long-tail extends to 12-hour streams. Storage: exabyte-scale corpus.
Latency: Time-to-first-frame p99 < 2 seconds (the user pressed play; they're waiting). Adaptive bitrate decisions in <1 second. Live latency: 5-30 seconds is standard; <2 seconds is 'low-latency' tier (much harder).
Availability: 99.99% on playback. A 5-minute outage during a live event is catastrophic. Upload availability can be lower (99.9%); users will retry.
Consistency: Eventually consistent. A new upload appears in search within minutes. Watch progress syncs eventually across devices.

The full walkthrough covers

Architecture components

·Upload service
·Transcode workflow orchestrator
·Transcode worker pool
·Object storage
·Manifest service
·CDN (origin + edge)
·Live ingestion gateway
·Live transcoder
·Watch service
·Analytics pipeline

Deep dives

The encoding ladder: what to encode and why
Adaptive bitrate (HLS / DASH)
CDN economics and global delivery
Live streaming: a different beast
Storage tiering and the long-tail
Search, discovery, and recommendations

What's in the full walkthrough

Capacity estimation · architecture with all 10 components explained · 6 deep dives · trade-off analysis · 8 common follow-up questions

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Streaming

Design a Video Streaming Service (YouTube / Netflix)

Hard Premium

Encoding ladders, adaptive bitrate, CDN economics, and the difference between live and VOD. Petabyte-scale storage meets millisecond-scale playback.

The problem

Clarifying questions

Asking these before diving into a solution is the difference between a "hire" and a "no signal" rating. Pick the questions whose answers would change your design.

→Are we designing VOD, live, or both? They share storage but diverge sharply on the playback path.
→What's the upload volume - hours of video per day? Average video length?
→How many concurrent viewers at peak - 1M? 100M? The CDN strategy depends sharply.
→What qualities do we serve - SD, HD, 4K? Mobile-only?
→Are we serving global users (CDN strategy is critical) or single-region?
→What's the latency budget for live - 30 seconds is acceptable, sub-second (low-latency live) is much harder?
→Do we need DRM, watermarking, geo-blocking?
→Monetization model - ads (which inject mid-stream), subscription, free?

Requirements

Functional requirements

·Upload video file or live stream
·Transcode into multiple qualities (encoding ladder)
·Generate streaming manifest (HLS or DASH)
·Stream video to client with adaptive bitrate
·Generate thumbnails, previews, scrub-bar art
·Serve via global CDN with low first-byte latency
·Track watch progress, recommendations input

Non-functional requirements

Scale: 1B DAU. 500 hours of video uploaded per minute (YouTube-scale). 100B watch events per day. Average video length 10 minutes; long-tail extends to 12-hour streams. Storage: exabyte-scale corpus.
Latency: Time-to-first-frame p99 < 2 seconds (the user pressed play; they're waiting). Adaptive bitrate decisions in <1 second. Live latency: 5-30 seconds is standard; <2 seconds is 'low-latency' tier (much harder).
Availability: 99.99% on playback. A 5-minute outage during a live event is catastrophic. Upload availability can be lower (99.9%); users will retry.
Consistency: Eventually consistent. A new upload appears in search within minutes. Watch progress syncs eventually across devices.

The full walkthrough covers

Architecture components

·Upload service
·Transcode workflow orchestrator
·Transcode worker pool
·Object storage
·Manifest service
·CDN (origin + edge)
·Live ingestion gateway
·Live transcoder
·Watch service
·Analytics pipeline

Deep dives

The encoding ladder: what to encode and why
Adaptive bitrate (HLS / DASH)
CDN economics and global delivery
Live streaming: a different beast
Storage tiering and the long-tail
Search, discovery, and recommendations

What's in the full walkthrough

Capacity estimation · architecture with all 10 components explained · 6 deep dives · trade-off analysis · 8 common follow-up questions

Subscribe to Continue

Get full access to gitGood.dev with a subscription.

Start Your 10-Day Trial

Try everything free for 10 days. Cancel anytime.

1,950+ practice questions
AI mock interviews (3/day)
Coding challenges with real execution
Verified skill badges
146 certification guides, 26 with practice exams

View Plans

10-day trial, then $5/mo - or $40/yr ($3.33/mo, save 33%). Cancel anytime.

Companies that test this topic

Practice in interview format

Start an AI mock interview →

Design a Video Streaming Service (YouTube / Netflix)

The problem

Clarifying questions

Requirements

Functional requirements

Non-functional requirements

The full walkthrough covers

Architecture components

Deep dives

What's in the full walkthrough

Subscribe to Continue

Start Your 10-Day Trial

Related system design topics

Distributed Cache

News Feed

Companies that test this topic

Practice in interview format

Design a Video Streaming Service (YouTube / Netflix)

The problem

Clarifying questions

Requirements

Functional requirements

Non-functional requirements

The full walkthrough covers

Architecture components

Deep dives

What's in the full walkthrough

Subscribe to Continue

Start Your 10-Day Trial

Related system design topics

Distributed Cache

News Feed

Companies that test this topic

Practice in interview format