Notification platform: understand it, then design it

Day 1 of the notification platform: how to open the interview with FERNS, the clarifying dialogue and the requirements read back, priorities and channel trade-offs, the channel selector and quiet hours, compliance penalties and rules, traffic, storage and provider cost, then the architecture, one notification traced end to end and through a push failure, why Kafka, the data layer, and idempotent, versioned APIs.