← Lessons

quiz vs the machine

Gold1430

System Design

The Notification Delivery Pipeline

Moving an event through filtering, formatting, and channel selection so the right user gets the right message.

5 min read · core · beat Gold to climb

What it is

A notification delivery pipeline turns a raw event into a message a person actually receives. Between the event and the inbox sit several stages that decide whether, how, and where to deliver.

The stages

  • Trigger: an event such as a new comment enters the pipeline.
  • Preferences: the user settings decide if they even want this notification.
  • Formatting: the event becomes readable text for the chosen channel.
  • Channel selection: the message is routed to in app, email, or push.

Why staging matters

Each stage is a place to drop noise. Preference checks suppress unwanted alerts, deduplication collapses repeats, and rate limiting stops a flood. Separating stages also lets each scale and fail independently.

Reliability

  • Persist the event so a crash mid pipeline can retry from a known stage.
  • Make delivery idempotent so a retry does not send a duplicate notification.

Key idea

A notification delivery pipeline routes an event through preference checks, formatting, and channel selection, with each stage able to suppress noise and retry safely on failure.

Check yourself

Answer to earn rating on the learn ladder.

1. What is the purpose of the preference stage in the pipeline?

2. Why should delivery be idempotent?