Disaster Recovery by Objectives: RTO, RPO, and DR Patterns
Disaster recovery planning starts by eliciting the Recovery Time Objective (RTO) and Recovery Point Objective (RPO) before picking a pattern. This interactive lesson maps four DR patterns to storefront objectives and defends warm standby. Covers: Backup and restore, pilot light, warm standby, active-active, multi-AZ versus Region recovery, browse-only mode, failover decisions, DR tests, failback. Prerequisites: Availability Zones, Regions, and data replication.
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An interviewer asks how the storefront would survive a Region-wide outage. We haven't been given a recovery timeline or an existing disaster recovery plan yet, so we can't choose an architecture. The interviewer's constraint is clear: a multi-Availability Zone design protects against many local failures, but it does not recover the checkout path when an entire AWS Region is unavailable.
When asked, “What’s your DR plan if the whole Region goes down?”, begin with requirements rather than naming the most available pattern. Recovery Time Objective (RTO) is the maximum acceptable time to restore a service after disruption. Recovery Point Objective (RPO) is the maximum acceptable data loss measured in time.
Elicit the recovery objectives
Let’s ask, ...