design_diagram.md

Initial Requirements (100,000 users/hour):

• Concurrent streams: ~28,000 (assuming 10-minute average watch time)

• Storage needed:

  • Daily Active users (DAU): 2,400,000 (100k/hr)
  • Average video uploaded per user per day: 0.005 videos (0.5 % of DAUs upload a video daily)
  • Average video size: 100 MB (at 1080p resolution, H264 compression)
  • Daily uploads: 2,400,000 x 0.005 = 12,000 videos/day
  • Daily storage for uploads: 12,000 x 100 MB = 1.2 TB/day
  • Annual video uploads: 1.2 TB/day x 365 days = 438 TB/year
  • With 3× replication: 438 TB x 3 = 1.314 PB/year

• Chunk operations:

• 100 MB video = (64 - 256 MB each)

System Scaling Projections - After 12 months (10% monthly growth): TODO recalculate

• Users: 100,000 × (1.10)¹² ≈ 314,000 users/hour
• Storage: 45 PB × 3.14 ≈ 141 PB
• Monthly uploads: 314,000 videos = 4.71 billion chunks

Adaptive Bitrate Streaming (ABS)

Type           Video bitrate 24, 25, 30 fsp
2160p (4k)     35,000-45,000 kbps
1440p (2k)     16,000 kbps
1080p (HD)      8,000 kpps
720p            5,000 kbps
480p            2,500 kbps
360p            1000 kbps

• On-Demand

• HTTP Streaming (HLS)

• Dynamic Adaptive Streaming over HTTP (DASH)

• LIVE

• RTMP

• DASH

Video Assets -> Transcoder => (Bitrate Variants) => MPEG-DASH Package and Encryption -> DASH MPD and chunks on OS -> CDN -> <--Request/Serve Video Segments and MPD --> MPEG-DASH Video Player

• Functional Requirements Non Functional Requirements
• Video Upload - Low latency: the system should allow users to upload video files with various formats and sizes, efficiently and securely, this includes handling large files providing progresss feedback and supporting resumable uploads in case of interruptions
• Encoding and Transcoding - High Availability: the system needs to process and convert uploaded videos into multiple standardized formats and resolutions, this ensures compatibility across different devices and network conditions, enabling smooth playback for all users
• Streaming Video Content- High Scalability: the system should also enable users to stream video content seamlessly, it must support adaptive bit rate streaming to adjust video quality in real time based on the user's network speed and device capabilities as well as to minimize buffering and to ensure a high quality viewing experience.
• Notifications

graph TB
    %% Client Layer
    subgraph Client Layer
        UD[User Dashboard<br/>- Video Player<br/>- Search Bar<br/>- Watch History]
        CD[Creator Dashboard<br/>- Video Upload Interface<br/>- Content Management<br/>- Performance Metrics<br/>- Billing Management]
        AD[Admin Dashboard<br/>- System Analytics<br/>- User Management<br/>- Content Moderation]
    end

    %% CDN Layer
    subgraph CDNLayer [CDN & Edge Network]
        CDN[Content Delivery Network<br/>- Edge Caching<br/>- Geographic Distribution<br/>- Cache Invalidation]
        
        subgraph EdgeLocations [Edge Locations]
            EL1[Edge Location<br/>US-East]
            EL2[Edge Location<br/>EU-Central]
            EL3[Edge Location<br/>AP-South]
        end
    end

    %% Application Layer
    subgraph Application Layer
        API[API Gateway / Load Balancer<br/>Routing, Rate Limitting, Auth]
        
        subgraph UserFacingServices [User-Facing Services]
            VSS[Video Streaming Service]
            SS[Search Service]
            UHS[User History Service]
        end
        
        subgraph CreatorFacingServices [Creator-Facing Services]
            VUS[Video Upload Service]
            CCS[Creator Content Service]
        end
    end

    %% Service Layer
    subgraph Service Layer
        AUTH[Authentication &<br/>Authorization Service]
        VPP[Video Processing Pipeline<br/>Transcoding, Thumbnails]
        AMS[Analytics & Metrics Service]
        NS[Notification Service]
        SIS[Search Indexing Service]
        BILL[Billing API Service<br/>- Payments<br/>- Subscriptions<br/>- Payouts]
        CDNM[CDN Management Service<br/>- Cache Control<br/>- Purge Requests<br/>- Edge Analytics]
    end

    %% Data Storage Layer
    subgraph DataStorageLayer [Data Storage Layer]
        UDB[(User Database<br/>Users, Roles)]
        VMDB[(Video Metadata Database<br/>Titles, Tags, Descriptions)]
        OS[(Object Storage<br/>S3 - Video Files)]
        DW[(Metrics & Logs<br/>Data Warehouse)]
        HDB[(History Database<br/>Watch History)]
        SI[(Search Index<br/>Elasticsearch)]
        BDB[(Billing Database<br/>Transactions, Subscriptions)]
    end

    %% Connections

    %% Client to CDN Layer
    UD --> CDN
    CD --> EL1
    CD --> EL2
    CD --> EL3

    %% CDN to Application Layer
    CDN --> API
    EL1 --> VSS
    EL2 --> VSS
    EL3 --> VSS

    %% Application Layer Internal
    API --> VSS
    API --> SS
    API --> UHS
    API --> VUS
    API --> CCS
    API --> BILL
    API --> AUTH

    %% CDN to Storage (Cache Miss)
    CDN -.-> OS
    EL1 -.-> OS
    EL2 -.-> OS
    EL3 -.-> OS

    %% Services to Support Services
    VUS --> VPP
    CCS --> AUTH
    VSS --> AUTH
    VSS --> CDNM
    SS --> SIS
    UHS --> AMS
    BILL --> AUTH
    CDNM --> AMS

    %% Support Services to Data Storage
    AUTH --> UDB
    VPP --> VMDB
    VPP --> OS
    AMS --> DW
    SIS --> SI
    BILL --> BDB
    CDNM --> VMDB
    
    %% Services to Data Storage
    VSS --> VMDB
    VSS --> OS
    SS --> SI
    UHS --> HDB
    CCS --> VMDB
    VUS --> VMDB

    %% Additional connections for completeness
    VPP --> SIS
    CCS --> OS
    AMS --> VMDB
    BILL --> UDB
    BILL --> DW

    %% CDN Management connections
    CDNM --> CDN
    VPP --> CDNM

    %% Styling
    classDef clientLayer fill:#e1f5fe, stroke:#01579b, stroke-width:2px
    classDef cdnLayer fill:#fff8e1, stroke:#ff6f00, stroke-width:2px
    classDef appLayer fill:#f3e5f5, stroke:#4a148c, stroke-width:2px
    classDef serviceLayer fill:#e8f5e8, stroke:#1b5e20, stroke-width:2px
    classDef storageLayer fill:#fff3e0, stroke:#e65100, stroke-width:2px
    
    class UD,CD,AD clientLayer
    class CDN,EL1,EL2,EL3 cdnLayer
    class API,VSS,SS,UHS,VUS,CCS appLayer
    class AUTH,VPP,AMS,NS,SIS,BILL,CDNM serviceLayer
    class UDB,VMDB,OS,DW,HDB,SI,BDB storageLayer

Loading

CDN Layer

• CDN Management Service: Handles cache control, purge requests, and edge analytics
• Edge Locations: Geographic distribution for low-latency content delivery
• Main CDN Node: Central CDN coordination

Data Flow

Cache Behavior

• Solid lines: Primary request flow (cache hits)
• Dashed lines: Secondary flow (cache misses, background operations)
• Edge Locations: Serve cached content to regional users

Fault Tolerance:

• Automatic failure detection via heartbeats
• Data durability through chunk re-replication
• Consistency via quorum reads/writes
• Recovery through checkpointing and Write Ahead Logs (WAL)
• Leadership coordination through election
• Geographic Redundancy: Multiple edge locations provide failover
• Cache Resilience: Users can continue watching cached content during origin outages
• Graceful Degradation: CDN serves stale content if origin is unavailable

Video Streaming Fault Tolerance

• Availability
• P

Video Upload Fault Tolerance

• Consistency
• P

API Endpoints

• Authentication and Authorization Service

POST /auth/login
POST /auth/logout
POST /auth/refresh-token

• User-Facing Services

• Search Service

• User History Service

• Creator-Facing Services

• Creator Content Service

• Billing Service

• Payment Processing

• Creator Payouts

• Admin Services

• Analytics and Metrics

• Notification Services

• External Service Endpoints

• CDN Service

POST /cdn/purge/{videoId}          # Invalidate cached video
GET  /cdn/analytics/edge-stats     # Get CDN performance metrics
POST /cdn/fetch/{videoId}       # Calculate cache for anticipated demand
GET  /cdn/cache-status/{videoId}   # Check cache status across edges