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Difficulty: HardDisaster Recovery and Business Continuity Execution

An enterprise healthcare logistics platform operates its primary inventory and ordering engine on Cloud SQL for MySQL in `europe-west1`, fronted by a Compute Engine Managed Instance Group (MIG). The architecture team must establish a disaster recovery (DR) execution plan to recover application operations in `europe-west4` during a catastrophic regional outage. Business continuity requirements specify a Recovery Point Objective (RPO) of ≤5 minutes\le 5\text{ minutes} and a Recovery Time Objective (RTO) of ≤15 minutes\le 15\text{ minutes}, while strictly minimizing idle infrastructure costs during standard operations. Which execution strategy meets all technical and business constraints?

  1. A
    Migrate the inventory database from Cloud SQL to a multi-region Cloud Spanner instance spanning `europe-west1` and `europe-west4`, while maintaining fully provisioned, active Compute Engine MIG capacity in both regions continuously.
  2. Maintain a cross-region asynchronous Cloud SQL read replica in `europe-west4`, pre-allocate regional compute quotas, and keep an unscaled MIG template ready. During failover, promote the replica to a primary database, scale out the MIG instance count, and update Cloud DNS routing.Answer
  3. C
    Provision a secondary MIG in `europe-west4` and route hybrid backend traffic through an existing VPC Network Peering connection established between `europe-west1` and the central hybrid transit VPC, avoiding a separate VPN or Interconnect in `europe-west4`.
  4. D
    Configure automated hourly Cloud SQL export dumps to a multi-region Cloud Storage bucket. Upon regional disaster declaration, restore the database from snapshot into `europe-west4` and request an emergency regional vCPU quota increase for compute scaling.

Answer

Maintain a cross-region asynchronous Cloud SQL read replica in the DR region with pre-allocated compute quotas and unscaled MIG instance templates. Upon disaster declaration, promote the replica, scale up the MIG, and update DNS routing.
The correct strategy uses a Cloud SQL cross-region read replica to continuously mirror state from `europe-west1` to `europe-west4`, satisfying the ≤5 minute\le 5\text{ minute} RPO. Pre-approved compute quota and automated MIG deployment templates allow compute capacity to scale on demand during a failover event within the 15-minute RTO, while keeping idle compute costs at near zero during normal operation.

Step-by-Step Solution

1
Analyze RPO requirements against data replication patterns.
An RPO ≤5 minutes\le 5\text{ minutes} requires continuous cross-region data replication. Asynchronous Cloud SQL cross-region read replicas meet this requirement with near-zero replication lag without requiring multi-region database refactoring.
Periodic export dumps (e.g., hourly) result in up to 60 minutes of data loss, violating the RPO boundary.
2
Analyze RTO requirements and cost constraints against compute failover topologies.
A pilot light or warm standby compute pattern with zero baseline running instances minimizes compute costs while keeping MIG templates ready.
Maintaining dual active compute clusters incurs high unnecessary operational expenses, while requesting quota during an emergency introduces unpredictable provisioning delays.
3
Evaluate network transitivity and DR execution dependency constraints.
Ensure direct regional interconnect/VPN connectivity and avoid reliance on non-transitive VPC Peering paths.
VPC Peering does not support transitive routing across multiple peered VPC networks.

Key Concept

Disaster Recovery Strategy Execution (Warm Standby / Pilot Light with Cloud SQL Cross-Region Replication)
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Topics

Disaster Recovery and Business Continuity Execution

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