How would you design a scalable notification system that handles millions of state changes per second without losing notifications?

hard📝 Trade-off Q9 of 15

LLD - Design — Online Shopping Cart

AUse synchronous direct calls to observers for immediate updates.

BUse asynchronous message queues to decouple state changes from notifications.

CStore all notifications in a database and poll observers periodically.

DUse a single-threaded loop to notify all observers sequentially.

Step-by-Step Solution

Solution:

Step 1: Identify scalability challenges
Millions of state changes require non-blocking, decoupled notification to avoid delays and loss.
Step 2: Choose asynchronous messaging
Message queues allow buffering and parallel processing, ensuring reliable delivery at scale.
Final Answer:
Use asynchronous message queues to decouple state changes from notifications. -> Option B
Quick Check:
High scale needs async queues [OK]

Quick Trick: Async queues handle high volume notifications [OK]

Common Mistakes:

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