AdvancedLesson 6

Disaster Recovery, RTO, RPO and Failover

ELI5 Explanation

If your main data center goes down, disaster recovery is your backup plan. RTO is how fast you must recover. RPO is how much data you can afford to lose.

Technical Explanation

DR design starts with business impact analysis, critical service tiers, recovery objectives, and failover architecture. RTO drives restoration speed requirements. RPO drives replication and backup frequency. Practice failovers regularly to validate runbooks and automation.

Visual

Primary Region
⇄
Secondary Region
→
Traffic Failover
→
Recovery Verified

Hands-on Commands

Backup and failover checks
kubectl get pvc -A
kubectl get volumesnapshot -A
kubectl get ingress -A
kubectl get deploy -A -o wide
# Example: simulate traffic switch in DNS/ingress controller workflow

Debugging Scenario

During a regional outage, app pods recover in secondary region but database lag exceeds RPO. Team executes read-only mode, restores from latest snapshot, then replays durable queue events to meet data integrity requirements.

Warning: Untested failover is a high-risk assumption, not a recovery strategy.

Beginner

  • What are RTO and RPO?
  • Why do we need DR plans?
  • Difference between backup and replication?
  • What is failover?
  • What is active-active vs active-passive?

Intermediate

  • How do you define service tiers for DR?
  • How do you test failover safely?
  • How does DNS TTL affect failover speed?
  • How do you handle stateful recovery in Kubernetes?
  • How do you estimate DR cost vs risk?

Scenario-based

  • RTO target is 15 minutes, current failover is 40. What changes first?
  • Secondary region is healthy but data is stale. What decision framework do you use?
  • Backup restore succeeded but app still fails. What dependency checks follow?
  • Traffic split causes partial outage during failback. How do you stage recovery?
  • Auditors request DR evidence. What artifacts do you provide?

Real-world Use Case

A healthcare platform moved from weekly backups to continuous replication for patient scheduling services. Recovery objectives improved from RTO 4 hours / RPO 24 hours to RTO 20 minutes / RPO 5 minutes.

Summary

Disaster recovery needs architecture, automation, and rehearsal. Next, you will learn chaos engineering to proactively test resilience before real disasters happen.

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