Problem
Design a multi-tenant notification/messaging system. Multiple companies use the service, each needing several delivery modes and priority control.
Requirements
- Multiple channels: SMS, email, push, etc.
- Per-company and per-message-type priority management
- Tenant isolation across companies
Discussion points
- Pluggable channel providers behind a common interface
- Priority queues and per-tenant rate limiting
- Retries, fallbacks, and delivery tracking