System Design FAQ: Top Questions

A Video Streaming Platform allows users to upload, encode, store, and stream videos on-demand or live. It must deliver high performance, fault tolerance, and adaptability to varying network conditions.

📋 Functional Requirements

• Upload and store video content
• Stream videos with adaptive quality
• Support recommendations, comments, and metadata

📦 Non-Functional Requirements

• High availability and performance
• Scalable to millions of users
• Low latency and buffering time

🏗️ High-Level Architecture

• Frontend: HTML5 video player, video search UI
• Upload Service: Accepts and validates video files
• Encoding Service: Transcodes videos into multiple resolutions
• CDN: Delivers video chunks globally with low latency
• Storage: Blob store like AWS S3 for original and encoded files
• Database: Stores metadata (PostgreSQL, DynamoDB)

🎬 Video Transcoding Pipeline

1. Upload triggers a message to SQS/Kafka
2. Encoding jobs transcode into 240p, 480p, 720p, 1080p
3. Save HLS (HTTP Live Streaming) segments to S3

🔧 FFmpeg Command Example

ffmpeg -i input.mp4 -profile:v baseline -level 3.0 -s 640x360 -start_number 0 \
  -hls_time 10 -hls_list_size 0 -f hls 360p.m3u8
        

🌍 CDN Caching (CloudFront example)

• Cache HLS segments (.ts) and playlists (.m3u8)
• Edge-optimized delivery with signed URLs

🗃️ Video Metadata Table

CREATE TABLE videos (
  video_id UUID PRIMARY KEY,
  title TEXT,
  user_id UUID,
  description TEXT,
  resolutions TEXT[],
  upload_time TIMESTAMP,
  views BIGINT DEFAULT 0,
  duration INT
);
        

📈 Observability Metrics

• Encoding latency and success rates
• Stream start time and buffer underruns
• Cache hit ratio from CDN

☁️ Cloud Services

• Storage: AWS S3, Google Cloud Storage
• Transcoding: AWS MediaConvert, FFmpeg
• Streaming: CloudFront, Akamai, Cloudflare

📌 Final Insight

Designing a video streaming system requires balancing latency, bandwidth, and scalability. Preprocessing via encoding, segmenting for adaptive bitrate streaming, and using CDNs for global delivery are key to a seamless video experience.