Where the system ends

The alert-processor (L15) calls notifyClient.Send(event) to deliver an alert. Open pkg/notification expecting Slack/email/PagerDuty routing… and you find one small file. That's the lesson. The actual channels live in a separate service; this package is just a resilient HTTP client to it. The final thing to understand about risk-graph-indexer is where it stops.

1 · The boundary

pkg/notification is the seam. Its entire job is to hand a correctly-shaped message across that wall over HTTP. The code even says so: NotificationRequest "matches the ChainWorkerMessage schema from forta-attester … fields and JSON tags must match exactly for the notification service to accept it."

2 · It's an adapter (anti-corruption layer)

Send doesn't just forward the event — it translates the system's internal AlertEvent into the external service's schema (client.go):

This translation layer is an anti-corruption layer: the external service's wire format never leaks into the risk engine, and a change on either side is absorbed here. The two domains stay decoupled.

3 · Resilient by construction

The send is small but production-hardened — a compact tour of the patterns you've met:

// pkg/notification/client.go — Send (the retry loop)
for attempt := range c.maxRetries {
    if ctx.Err() != nil { return false }       // honour cancellation/shutdown
    if err := c.doPost(ctx, body); err == nil {
        return true                          // delivered → L15 marks Delivered=true
    }
    if attempt < c.maxRetries-1 {
        backoff := time.Duration(1<<uint(attempt)) * time.Second  // 1s, 2s, 4s, 8s…
        select {
        case <-time.After(backoff):                // wait…
        case <-ctx.Done(): return false            // …unless cancelled mid-wait
        }
    }
}
return false  // all retries exhausted → L15 marks Delivered=false (recoverable)

Check yourself

What you can now do

• Explain that delivery channels live in an external service; pkg/notification is just the resilient HTTP seam.
• Describe the boundary: this system decides what to alert, forta-attester decides how to deliver.
• Recognise Send as an adapter / anti-corruption layer, and FFRId as a cross-boundary idempotency key.
• Read the exponential-backoff + context-cancellable retry loop and connect Send's bool to L15's Delivered flag.
• Articulate why knowing where a system ends is a feature, not a gap.