Notification system
Push, email and SMS from one place: templates, preferences, retries and no duplicates.
What is on this board
Parts
- Any service Service
- Notifications API Service
- Preferences and templates Relational DB
- Per person Rate limiter
- One queue per channel Message queue · SQS
- Push workers Worker pool
- Email workers Worker pool
- SMS workers Worker pool
- APNs and FCM External API
- Email Email / SMS / push · Resend
- SMS Email / SMS / push · Twilio
- Failed Dead-letter queue
- What was sent Audit log
- At least once, deduplicated Decision record
How they connect
- Any service → Notifications API: order shipped
- Notifications API → Preferences and templates: does she want this?
- Notifications API → Per person: too many today?
- Notifications API → One queue per channel: send
- One queue per channel → Push workers: push
- One queue per channel → Email workers: email
- One queue per channel → SMS workers: sms
- Push workers → APNs and FCM: send
- Email workers → Email: send
- SMS workers → SMS: send
- Push workers → Failed: gave up
- Push workers → What was sent: sent
Notes and decisions
- Any service: Says what happened, not how to tell people
- Per person: Nobody wants 50 pushes
- What was sent: Also the idempotency key
- At least once, deduplicated: Providers fail, so we retry. An idempotency key per notification stops the second copy.
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