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PCDE Practice Question: Deploy scalable and highly available databases in Google Cloud
A company runs a Cloud Bigtable instance with two clusters in separate regions for disaster recovery. They want to ensure that read requests automatically use the secondary cluster if the primary cluster becomes unhealthy. Which two steps should they take? (Choose two.)
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Change the routing policy to 'cluster-group routing' (any-replica)
To enable automatic failover for reads in Bigtable, you need to use a routing policy that distributes reads across clusters. The 'cluster-group routing' (also called 'any-replica' routing) automatically routes requests to the nearest healthy cluster. Additionally, you must configure the application to use this routing policy. Alternatively, you can use a load balancer with health checks, but that is not native to Bigtable. The correct native approach is to use cluster-group routing and ensure the application uses it.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Change the routing policy to 'cluster-group routing' (any-replica)
Why this is correct
Cluster-group routing automatically sends reads to any available cluster, providing failover.
- ✓
Ensure the application uses the 'any-replica' routing policy in the client configuration
Why this is correct
The application must be configured to use the routing policy; using 'any-replica' (cluster-group routing) enables automatic read failover.
- ✗
Set up a load balancer in front of Bigtable instances
Why it's wrong here
Bigtable is accessed via gRPC; putting a load balancer in front is not supported natively.
- ✗
Create a third cluster in a third region for quorum
Why it's wrong here
Additional clusters are not required for failover; two clusters are sufficient.
- ✗
Configure Cloud DNS with a health check that points to the secondary cluster
Why it's wrong here
Cloud DNS health checks can be used to route traffic, but Bigtable applications typically connect directly to the Bigtable endpoint; this is not a standard Bigtable failover method.
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Same concept, more angles
3 more ways this is tested on PCDE
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Variation 1. A company uses Cloud Bigtable with two clusters in different regions for disaster recovery. They need to ensure that if the primary cluster becomes unavailable, read traffic is automatically redirected to the secondary cluster with minimal manual intervention. Which three actions should they take? (Choose THREE)
medium- ✓ A.Enable multi-cluster replication between the clusters
- ✓ B.Set up Cloud DNS with a health check to detect cluster health and update DNS records accordingly
- ✓ C.Configure the Bigtable routing policy to 'any-replica' or 'read-failover'
- D.Add read-only replicas to the secondary cluster
- E.Configure a write failback policy to switch write clusters
Why A: To achieve automatic failover for Bigtable reads, you need: (1) multi-cluster replication enabled, (2) a routing policy that supports failover (read-failover or any-replica with health checking), and (3) an external health check mechanism (like Cloud DNS health checks) to redirect client traffic if the primary cluster is unhealthy. Option D (write failback) is not relevant for reads. Option E (read-only replicas) is not applicable as Bigtable doesn't have that concept.
Variation 2. A media company uses Cloud Bigtable to serve user recommendations with low latency. They want to implement disaster recovery with a secondary cluster in a different region. They need automatic failover without manual DNS changes. Which routing policy should they configure?
medium- A.Enable any-replica routing policy on the Bigtable cluster
- B.Use single-cluster routing with manual DNS failover
- C.Implement application-managed routing with a custom health check
- ✓ D.Configure read-failover routing policy and use Cloud DNS health checks
Why D: The read-failover policy uses health checks to automatically route traffic to the secondary cluster if the primary becomes unhealthy. Any-replica sends requests to the closest cluster regardless of health. Manual DNS changes would be required for any-replica after a failure. Application-managed routing is not a built-in Bigtable feature.
Variation 3. A company is planning disaster recovery for Bigtable. They have two clusters in different regions with replication enabled. They want to automate failover using Cloud DNS. Which THREE components are required for this automation? (Choose 3)
medium- A.Bigtable replication routing policy set to any-replica.
- B.Cloud Bigtable AppProfile with single-cluster routing.
- ✓ C.Cloud HTTP(S) health check for the Bigtable cluster endpoints.
- ✓ D.Cloud Functions to update the DNS record on health check failure.
- ✓ E.Cloud DNS managed zone with a weighted routing policy.
Why C: To automate Bigtable failover, you need a Cloud HTTP(S) health check to monitor the primary cluster, a Cloud DNS routing policy (e.g., weighted round robin) that can be updated, and a mechanism (e.g., Cloud Functions or an external tool) to update the DNS record when the health check fails.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCDE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCDE exam.