Designing a global high-throughput messaging app

Create a design for a globally accessible messaging system that supports group chats, can handle a massive volume of traffic, and ensures 99.99% uptime.

1. Develop an architectural diagram of the messenger considering global accessibility.
2. Identify key subsystems (message processing servers, media file storage, databases, caching layers, etc.).
3. Develop a scaling strategy for user base growth and load.
4. Ensure high availability (HA) and fault tolerance.
5. Describe the message processing flow: asynchronous operations, storage, delivery.

Expected load parameters:

• 700 million unique users per month;
• 60 million active users daily;
• an average of 15 messages per day per user;
• maximum text message size — 4096 characters;
• maximum upload file size — 2 GB.