Advanced
System Design
Q92 / 100
In designing a chat application supporting millions of concurrent users, why might "sticky sessions" with WebSocket connections create challenges for horizontal scaling?
Correct! Well done.
Incorrect.
The correct answer is A) Because a client keeps a persistent connection to one server instance, scaling must route messages to the instance holding that connection, often via a message broker or presence service
A
Correct Answer
Because a client keeps a persistent connection to one server instance, scaling must route messages to the instance holding that connection, often via a message broker or presence service
Explanation
Since WebSocket connections are stateful and tied to a specific server, delivering a message to a user requires knowing which instance holds their connection — often solved with a pub/sub layer (e.g., Redis Pub/Sub) so any instance can publish to the right one.
Progress
92/100