Triggered Email Sequences (Welcome, Abandoned Cart, Reactivation)

Developing Triggered Email Sequences (Welcome, Abandoned Cart)

Triggered sequences are chains of emails that start automatically in response to user action. Welcome series, abandoned cart, re-engagement, onboarding tips. Each email is sent at the right moment, not on schedule.

Architecture

Typical scheme: application publishes events → worker processes and queues tasks with delay → tasks execute email sends.

User action → App Event → Queue (BullMQ) → Email Worker → ESP (Resend/SendGrid)
                   ↓
             Sequence Engine
         (tracks progress,
          checks conditions)

Implementation with BullMQ

npm install bullmq ioredis

import { Queue, Worker, Job } from 'bullmq';
import Redis from 'ioredis';

const connection = new Redis(process.env.REDIS_URL);
const emailQueue = new Queue('email-sequences', { connection });

// Start welcome sequence
async function startWelcomeSequence(userId: string, email: string, name: string) {
  const baseData = { userId, email, name };

  // Email 1: immediately after registration
  await emailQueue.add('welcome-step-1', baseData, {
    delay: 0,
    jobId: `welcome-1-${userId}`,  // deduplication
  });

  // Email 2: after 1 day — how to use product
  await emailQueue.add('welcome-step-2', baseData, {
    delay: 24 * 60 * 60 * 1000,
    jobId: `welcome-2-${userId}`,
  });

  // Email 3: after 3 days — use case examples
  await emailQueue.add('welcome-step-3', baseData, {
    delay: 3 * 24 * 60 * 60 * 1000,
    jobId: `welcome-3-${userId}`,
  });

  // Email 4: after 7 days — if not activated — reminder
  await emailQueue.add('welcome-step-4', baseData, {
    delay: 7 * 24 * 60 * 60 * 1000,
    jobId: `welcome-4-${userId}`,
  });
}

Worker with Conditions

const worker = new Worker(
  'email-sequences',
  async (job: Job) => {
    const { userId, email, name } = job.data;

    // Check user hasn't unsubscribed
    const user = await db.users.findById(userId);
    if (!user || user.unsubscribed) return;

    switch (job.name) {
      case 'welcome-step-1':
        await sendEmail({
          to: email,
          templateId: 'welcome-01-greeting',
          data: { name },
        });
        break;

      case 'welcome-step-2':
        await sendEmail({
          to: email,
          templateId: 'welcome-02-getting-started',
          data: { name, dashboardUrl: `https://app.example.com/dashboard` },
        });
        break;

      case 'welcome-step-4':
        // Send only if user hasn't created any projects
        const projectCount = await db.projects.countByUser(userId);
        if (projectCount > 0) return;  // skip — already active

        await sendEmail({
          to: email,
          templateId: 'welcome-04-reminder',
          data: { name },
        });
        break;

Timeline

Implementing welcome and abandoned cart sequences — 2–3 days.