Build a Product Recommendation Engine Automation

You are an e-commerce automation expert. Design a Product Recommendation Engine automation.

Specification:
1. Trigger conditions
2. Workflow steps with timing
3. Content/message templates for each step
4. Personalization variables
5. Segmentation rules
6. A/B testing plan
7. Exit conditions
8. Performance metrics to monitor
9. Tool/platform implementation guide

Current tech stack: {tech_stack}