Zoom / Google Meet — Simple

Problem statement (interviewer prompt)

Design Zoom / Google Meet: real-time A/V conferencing for 2 to 1000 participants per meeting. Cover signaling, NAT traversal (STUN/TURN/ICE), SFU forwarding, simulcast/SVC, screen share, recording + live captioning, and optional E2E encryption.

flowchart LR
  A([User A])
  B([User B])
  SIG[Signaling Server]
  SFU[SFU - media forwarding]
  STUN[STUN / TURN]
  A --> SIG --> B
  A <--> STUN
  B <--> STUN
  A <--> SFU
  B <--> SFU

    classDef client fill:#dbeafe,stroke:#1e40af,stroke-width:1px,color:#0f172a;
    classDef edge fill:#cffafe,stroke:#0e7490,stroke-width:1px,color:#0f172a;
    classDef service fill:#fef3c7,stroke:#92400e,stroke-width:1px,color:#0f172a;
    classDef datastore fill:#fee2e2,stroke:#991b1b,stroke-width:1px,color:#0f172a;
    classDef cache fill:#fed7aa,stroke:#9a3412,stroke-width:1px,color:#0f172a;
    classDef queue fill:#ede9fe,stroke:#5b21b6,stroke-width:1px,color:#0f172a;
    classDef compute fill:#d1fae5,stroke:#065f46,stroke-width:1px,color:#0f172a;
    classDef storage fill:#e5e7eb,stroke:#374151,stroke-width:1px,color:#0f172a;
    classDef external fill:#fce7f3,stroke:#9d174d,stroke-width:1px,color:#0f172a;
    classDef obs fill:#f3e8ff,stroke:#6b21a8,stroke-width:1px,color:#0f172a;
    class A,B client;
    class SIG,SFU,STUN service;