The multi-channel part is where I spent most of my time and probably where I fumbled a bit.
Start by clarifying requirements and scale, then design a decoupled, event-driven architecture with a notification service that handles both single and bulk sends. Focus on channel abstraction, idempotency, and reliability, and discuss trade-offs like synchronous vs. asynchronous processing and prioritization.
Pro tip: Emphasize idempotency and deduplication for bulk sends to avoid spamming users, and mention how you would handle failures with retries and dead-letter queues. Also, consider user preferences and rate limiting to respect user attention.
Ask about expected volume (e.g., millions of notifications per day), latency requirements, delivery guarantees, and supported channels. Clarify use cases like transactional vs. promotional and any compliance needs.
Propose a microservices-based system with a notification service that receives requests via API or events, processes them asynchronously using queues, and dispatches to channel-specific workers. Include a database for tracking and user preferences.
For single sends, use a direct API call that enqueues the notification. For bulk, accept a batch request, split into individual messages, and enqueue them, ensuring idempotency and deduplication.
Design a channel abstraction layer with adapters for SMS, push, email, and social. Each adapter handles provider-specific logic, rate limits, and retries. Use a common interface for sending.
Discuss using message queues (e.g., Kafka, SQS) for decoupling, retries with exponential backoff, dead-letter queues, and idempotent processing. Include monitoring, logging, and alerting for failures and latency.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.