PCDE Manage a solution that can span multiple database technologies Practice Test 3 — 15 Questions

Question 1

You need to monitor the replication lag between a Cloud SQL for MySQL primary instance and its read replica. Which metric should you use to set up an alert?

Accepted Answer

cloudsql.googleapis.com/database/replication/replication_lag. Cloud SQL exposes a metric 'replication/replication_lag' (or 'cloudsql.googleapis.com/database/replication/replication_lag') that measures the lag in seconds between the primary and replica. This is the correct metric for alerting.

Answer

cloudsql.googleapis.com/database/replication/replica_count

Answer

cloudsql.googleapis.com/database/cpu/utilization

Answer

cloudsql.googleapis.com/database/memory/utilization

Question 2

Your Firestore database in Native mode contains a collection with millions of documents. You need to query documents where the 'tags' field (an array) contains the string 'urgent'. What must you ensure in your index configuration?

Accepted Answer

No additional index configuration is required; Firestore automatically creates the necessary index for array fields.. Firestore automatically creates a single-field index for array fields. However, to query array-contains, you need an index on the field with the array-contains filter. Firestore automatically creates a single-field index for the 'tags' field, so no additional index is needed. If the query includes additional equality clauses, a composite index may be required, but for a simple array-contains, it's automatic.

Answer

Ensure the 'tags' field is not indexed, and then create a composite index with the array-contains filter.

Answer

Create an index exemption for the 'tags' field to enable array queries.

Answer

Create a composite index on 'tags' and '__name__' for the collection.

Question 3

Your company runs a global e-commerce platform on Cloud Spanner. You need to capture real-time changes to a table (e.g., orders) and stream them to a downstream analytics pipeline in near real-time. Which TWO Google Cloud features or services should you combine to achieve this? (Choose two.)

Accepted Answer

Dataflow streaming pipeline. A Dataflow streaming pipeline can consume Cloud Spanner change streams in near real-time, process the data (e.g., transform, filter, aggregate), and write it to a downstream analytics system. Dataflow provides exactly-once processing semantics and auto-scaling, making it ideal for continuous change data capture (CDC) pipelines.

Answer

Cloud Functions

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Cloud Pub/Sub

Answer

Cloud SQL for PostgreSQL

Question 4

You have a Memorystore for Redis instance used as a cache. You need to scale it to handle increased load. The current instance is Basic Tier with 2 GB memory. Which TWO actions can you take to scale the instance? (Choose two.)

Accepted Answer

Vertically scale the instance by increasing its memory size or changing to a higher-tier (e.g., Standard Tier).. Memorystore supports vertical scaling by increasing memory size or changing to a higher tier (e.g., Basic to Standard, or Standard to Standard with more memory) – this is option A. Horizontal scaling is achieved by enabling Redis Cluster, which automatically shards data across multiple nodes – this is option E. Option B (creating additional instances with client-side sharding) is not a supported scaling method for Memorystore because it requires manual management and is not integrated with the service. Option C (changing eviction policy to noeviction) does not scale the instance and risks data loss when memory is full. Option D (adding read replicas) is available only in Standard Tier, but it offloads read traffic, not scales the cache capacity.

Answer

Create additional instances and implement client-side sharding.

Answer

Change the eviction policy to noeviction to allow more data.

Answer

Add read replicas to offload read traffic.

Question 5

You are designing a disaster recovery plan for a Cloud Bigtable instance. The instance has a single cluster in us-east1. You need to ensure that if the cluster becomes unavailable, the database can still serve read and write requests with minimal downtime. Which THREE steps should you take? (Choose three.)

Accepted Answer

Ensure the application can handle eventual consistency between clusters.. Cloud Bigtable uses eventual consistency for replication across clusters. When you add a second cluster and enable replication, data is replicated asynchronously, so writes to one cluster are not immediately visible in the other. The application must be designed to handle eventual consistency to avoid reading stale data after a failover. Option C is correct: adding a second cluster in a different zone (within the same region or a different region) and enabling replication provides redundancy. If the primary cluster fails, the secondary cluster can serve requests. Option D is correct: the application must be configured to route traffic to the secondary cluster in case of primary failure. This can be achieved by using Cloud Bigtable's built-in failover mechanism or by implementing client-side routing logic. Without this routing, traffic would still be directed to the failed primary cluster, causing downtime.

Answer

Enable synchronous replication between clusters.

Answer

Take a full backup of the table to Cloud Storage daily.

Question 6

A company uses Cloud SQL for MySQL to run an e-commerce application. They need to ensure that they can recover the database to any point within the last 4 days. They also want to minimize storage costs. Which configuration should they use?

Accepted Answer

Enable binary logging with the 'log_bin' flag and set the transaction log retention to 4 days in the backup configuration.. Point-in-time recovery (PITR) in Cloud SQL for MySQL requires binary logging, which can be enabled with the 'log_bin' flag. The transaction log retention period can be set from 1 to 7 days. For 4-day recovery, set the retention to 4 days. Option B is correct: enable binary logging and set the transaction log retention to 4 days. Option A is wrong because automated backups alone only restore to backup time, not any point. Option C is wrong because disabling automated backups is not necessary—automated backups are still needed for initial restore points, but PITR uses transaction logs. Option D is wrong because point-in-time recovery is enabled by setting binary logging and retention; there is no separate 'point_in_time_recovery' flag.

Answer

Enable automated backups with a 4-day retention schedule.

Answer

Enable binary logging and set the transaction log retention to 4 days. Disable automated backups.

Answer

Enable point-in-time recovery by setting the 'point_in_time_recovery' flag to true with a 4-day window.

Question 7

A Cloud SQL for PostgreSQL instance is experiencing high read traffic. You need to offload read queries and ensure the solution can survive a regional outage. What should you do?

Accepted Answer

Create a cross-region read replica and direct read traffic to it.. Cross-region read replicas serve read traffic and provide disaster recovery if the primary fails. Creating a cross-region read replica reduces read load and can be promoted if the primary region fails. Option D is correct. Option A (Cloud Memorystore cache) reduces latency but does not survive a regional outage. Option B (increasing machine type) helps performance but not regional failover. Option C (same-region read replica) does not survive a regional outage.

Answer

Set up Cloud Memorystore as a cache in front of the database.

Answer

Increase the machine type of the primary instance to handle the load.

Answer

Create a read replica in the same region and use it for read queries.

Question 8

A Cloud SQL for MySQL instance is running out of storage. The team wants to increase storage automatically without manual intervention. However, they also want to control costs and avoid a sudden increase in storage beyond 1 TB. What should they do?

Accepted Answer

Enable auto-storage increase and set the maximum storage size to 1 TB.. Cloud SQL for MySQL provides an 'auto-storage increase' feature that automatically adds storage when usage is high. To control costs and prevent storage from exceeding 1 TB, you can enable this feature and set the maximum storage size to 1 TB. Option B is correct because it combines automation with a cost cap. Option A (using a Cloud Function) is more complex and not necessary since Cloud SQL has a built-in feature; it also doesn't guarantee a cap. Option C (manual resize) is not automated. Option D (enable auto-storage increase without setting a maximum) would allow storage to grow beyond 1 TB, failing the cost control requirement.

Answer

Set up a Cloud Function to monitor disk usage and resize the disk when needed.

Answer

Manually increase disk size by 10% each time usage reaches 80%.

Answer

Enable auto-storage increase; it automatically stops at 1 TB.

Question 9

A financial application uses Cloud Spanner and requires daily full backups stored in another region for compliance. The backups must be restorable without exporting/importing. Which backup method should they use?

Accepted Answer

Use Spanner's scheduled backups and configure a cross-region backup policy.. Spanner supports scheduled backups that can be configured for cross-region storage, allowing direct restoration to a new database without export/import. This meets the requirement of daily backups in another region with import-free restore. Option A (export to Avro files in Cloud Storage) requires import to restore, so it's incorrect. Option B (Cloud Scheduler triggering a script that takes a snapshot in Cloud Storage) is not a built-in Spanner feature and would require export/import, making it unsuitable. Option D (on-demand backups copied manually) is possible but not ideal for daily backups as it lacks automation.

Answer

Export the database to Avro files in Cloud Storage in another region, then import when needed.

Answer

Use Cloud Scheduler to trigger a script that takes a snapshot of the database in Cloud Storage.

Answer

Create on-demand backups and copy them to another region manually.

Question 10

A Cloud Bigtable instance is experiencing high read latency. The team suspects hot spotting on a single node. Which tool should they use to identify the hotspot?

Accepted Answer

Key Visualizer. Key Visualizer is the correct tool because it is specifically designed to analyze access patterns in Cloud Bigtable and identify hot spotting—where a small range of row keys receives a disproportionate amount of traffic. It visualizes read and write heatmaps across row key space and time, allowing teams to pinpoint the exact keys causing the hotspot. Unlike general-purpose monitoring tools, Key Visualizer provides row-key-level granularity essential for diagnosing hot spotting.

Answer

Cloud Logging to review request logs

Answer

Bigtable Admin API to list tables

Answer

Cloud Monitoring (Stackdriver) to check CPU utilization

Question 11

A Cloud Memorystore for Redis instance needs to ensure data is not lost during a maintenance event. The team decides to enable persistence. However, Memorystore does not support Redis persistence. What is the recommended alternative?

Accepted Answer

Use the Standard tier with replication and take regular snapshots to Cloud Storage using a scheduled script.. Cloud Memorystore for Redis does not support native Redis persistence (RDB or AOF). To prevent data loss during maintenance events, the recommended alternative is to use the Standard tier (which provides replication and automatic failover) and supplement it with scheduled snapshots exported to Cloud Storage. This approach ensures a durable backup outside the Redis instance that can be restored if needed.

Answer

Migrate to Cloud SQL for MySQL and use its backup feature.

Answer

Enable AOF persistence in Memorystore.

Answer

Increase the maxmemory setting and rely on the allkeys-lru eviction policy.

Question 12

A Cloud SQL for PostgreSQL instance has a read replica lagging behind the primary. The team needs to monitor the replica lag and set up an alert if it exceeds 60 seconds. Which metric should they use?

Accepted Answer

replication_lag. The correct metric is `replication_lag` because it directly measures the delay in seconds between the primary and read replica in Cloud SQL for PostgreSQL. This metric reflects how far behind the replica is in applying changes from the primary's write-ahead log (WAL), making it the precise indicator for alerting when lag exceeds 60 seconds.

Answer

bytes_received

Answer

disk_read_ops

Answer

cpu_utilization

Question 13

A Cloud Memorystore for Redis instance is running out of memory. The team wants to automatically remove the least recently used keys when memory is full. Which eviction policy should they configure?

Accepted Answer

allkeys-lru. The `allkeys-lru` eviction policy is correct because it applies the LRU (Least Recently Used) algorithm to all keys in the Redis instance, not just those with an expiry set. This ensures that when memory is full, the least recently accessed keys are automatically removed, regardless of whether they have a TTL, which directly meets the requirement to free memory without manual intervention.

Answer

volatile-lru

Answer

volatile-ttl

Answer

noeviction

Question 14

A company has a Cloud Bigtable cluster using HDD storage. They are migrating to a workload that requires lower latency, so they need to switch to SSD storage. How should they accomplish this?

Accepted Answer

Create a new Bigtable cluster with SSD storage in the same instance, replicate data, then delete the old cluster.. Cloud Bigtable does not support in-place conversion of storage type from HDD to SSD. The proper migration path is to create a new cluster with SSD storage within the same instance, enable replication to keep data synchronized, and then delete the old HDD cluster. This approach minimizes downtime and ensures data consistency.

Answer

Add more nodes to the existing cluster to improve latency.

Answer

Export data to Avro files, create a new SSD cluster, and import the data.

Answer

Modify the existing cluster's storage type to SSD using the Cloud Console.

Question 15

An application uses Cloud Firestore. The team notices that queries on a collection with an array field are slow. They want to create an index on the array field. What should they do?

Accepted Answer

Create a composite index on the array field and another field.. Cloud Firestore does not support single-field indexes on array fields. To enable efficient queries involving array fields, you must create a composite index that includes the array field along with another field. This allows Firestore to use the composite index for array-contains queries and other array operations, improving query performance.

Answer

Create a collection group index on the field.

Answer

Create an index exemption for the array field.

Answer

Rely on the automatically created single-field index.