Your question is Scale Multi-Channel Notifications. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
Design a notification system that can scale to send millions of multi-channel alerts (SMS, Email, Push) daily for Wise.
Clarify the alert types, recipient preferences, delivery guarantees, compliance requirements, and operational scale before proposing a design. Cover an end-to-end architecture, including event ingestion, notification selection, channel optimization, scheduling, provider integration, retries, observability, and ML evaluation where appropriate.