3.4. Reflection Checkpoint

Phase 3 covers one of the highest-stakes areas of the exam — reliability and business continuity together account for 22% of your score. Think of this phase like the load-bearing wall of your exam preparation: without a solid grasp of Auto Scaling policies, DR strategies, and failover mechanics, a large chunk of the exam becomes guesswork. Consider this: a candidate who confuses Multi-AZ with read replicas will answer availability and scaling questions incorrectly every time they appear, and they appear often. Unlike Phase 1's conceptual groundwork, Phase 3 tests specific configuration decisions under pressure — the difference between a 750 and an 850 often lives here.

Verify these before continuing:

1. What is the difference between a target tracking scaling policy and a step scaling policy? When do you prefer each?
2. An ASG is configured with health checks set to "EC2." The application on the instance has crashed, but the instance is still running. Does the ASG replace the instance? What change fixes this?
3. What is the difference between ElastiCache Redis and Memcached for session storage? Which is appropriate for production?
4. Route 53 Latency routing vs. Geolocation routing: what's the key difference and when do you use each?
5. RDS Multi-AZ: is the standby readable? What triggers automatic failover?
6. DynamoDB PITR: Is it enabled by default? What is the maximum restore window?
7. An S3 object was accidentally deleted. Versioning is enabled. How do you restore it?
8. A company needs RTO < 15 minutes and RPO < 5 minutes for a regional disaster. Which DR strategy fits, and can "Backup and Restore" meet these requirements?
9. What is AWS DRS, and what problem does it solve compared to standard snapshot-based backup?
10. What is the difference between S3 Object Lock Compliance mode and Governance mode?

💾 CHECKPOINT — Session 2 Complete Files saved: complete-guide.md (Phase 1 + Phase 2 + Phase 3), keywords.json, relationships.json Resume Point: Begin Phase 4 (Deployment, Provisioning, and Automation) in the next session.