Why don't large chat apps push every online/offline change to every member of big groups?

Options

• ✓ Each change goes to every member, so presence traffic grows with the square of the group's size Correct
• ✗ Presence cannot be stored
• ✗ WebSockets cannot carry presence
• ✗ Members' clocks disagree

Why

In a group of 10,000, each status change goes to 10,000 people, and all 10,000 members keep changing. Apps instead fetch presence lazily for the people on screen, or show it only in small groups.

Review this in your daily deck → All cards in Realtime