Design a Notification Service (Push, SMS, Email at Scale) | System Design Interview

How would you design a notification service that sends millions of push, SMS and email notifications reliably - without spamming users or sending duplicates? A complete, end-to-end system design interview answer - from requirements to scale. In this video: Functional and non-functional requirements for a notification system High-level architecture: notification API, message queues, channel workers and third-party providers (APNs, FCM, SMS, email) Notification flow end to end: trigger, template, user preferences, send, delivery status Reliability: retries with backoff, dead-letter queues and provider failover Deduplication and idempotency so users never get the same message twice Rate limiting, priorities, scheduling and user opt-out Scaling, monitoring and trade-offs Follow-up questions interviewers ask Who this is for: software engineers preparing for senior, staff or backend system design interviews. More from the channel: System Design Interview Questions: Complete Answers, Start to Finish (this playlist) System Design Interview - Scenario Based Questions Subscribe for more system design, AI engineering and coding interview tutorials. #SystemDesign #SystemDesignInterview #NotificationService #Kafka #DistributedSystems #Microservices #InterviewPrep