Last-engagement timestamp maintained

A last_engaged_at column that is never updated is worse than no column at all: it creates false confidence that engagement is being tracked while every contact's timestamp stays frozen at creation date. Stale-contact jobs keyed on last_engaged_at will then incorrectly classify all contacts as disengaged simultaneously, suppressing the entire list. The root cause is typically a webhook handler that logs events to an analytics table but does not write back to the contacts table — a common pattern in systems where the analytics pipeline was added after the contact model was built.

Wire ESP webhook open and click events directly to a contact last_engaged_at update — verify this write exists in the webhook handler, not just in an analytics sink:

// POST /api/webhooks/esp
export async function POST(req: Request) {
  const events = await req.json()

  for (const event of events) {
    if (['open', 'click'].includes(event.event)) {
      const email = event.email?.toLowerCase().trim()
      if (email) {
        await db.contact.updateMany({
          where: { email },
          data: {
            last_engaged_at: new Date(event.timestamp * 1000),
            engagement_tier: 'active'
          }
        })
      }
    }
  }

  return Response.json({ ok: true })
}

Validate HMAC signatures before processing events. After deploying, spot-check by triggering a test open through your ESP and confirming last_engaged_at updates on the corresponding contact row within minutes.