PCDE Manage a solution that can span multiple database technologies — Timed 10 Questions

Question 1

Your Cloud Bigtable instance is experiencing high latency for certain row key ranges. You suspect a hotspot is developing. Which Google Cloud tool should you use to visualize and diagnose the hotspot?

Accepted Answer

Key Visualiser. The Key Visualiser is a tool in the Google Cloud Console for Cloud Bigtable that provides a visual heatmap of row key access patterns, helping you identify hotspots and design better row keys. It shows read/write activity per row key range.

Answer

Cloud Monitoring dashboard to check CPU utilization per node

Answer

Bigtable's built-in 'hotspot detection' alert in Cloud Monitoring

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Cloud Logging to review request logs and identify slow queries

Question 2

You manage a Memorystore for Redis instance that is regularly hitting its maximum memory limit. The application can tolerate some data loss and prefers to keep the most recently used data. Which eviction policy should you configure?

Accepted Answer

volatile-lru. volatile-lru evicts keys with an expiry set (volatile keys) using an LRU (least recently used) algorithm. This fits the requirement: the application can tolerate loss of expired data, and it prefers to keep recently used data. allkeys-lru would evict any key, which might include important unexpired keys.

Answer

noeviction

Answer

volatile-ttl

Answer

allkeys-lru

Question 3

A Cloud SQL for MySQL instance is running low on disk space. You have enabled automatic storage increase, but you also want to be proactively alerted when disk usage exceeds 80%. Which steps should you take?

Accepted Answer

Create a Cloud Monitoring alert on the metric 'disk/utilization' with a threshold of 80%.. Cloud Monitoring is the native GCP observability service, and Cloud SQL exposes the 'cloudsql.googleapis.com/database/disk/utilization' metric. Creating an alerting policy on that metric with an 80% threshold and a notification channel (email, Pub/Sub, PagerDuty) is the standard, supported way to be proactively alerted. This works alongside automatic storage increase, which only reacts after usage grows.

Answer

Set the storage size to a fixed large value to avoid alerts.

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Create a Cloud Logging sink for disk usage logs and set up a Pub/Sub notification.

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Use Cloud SQL's built-in email notifications for disk usage.

Question 4

Your Memorystore for Redis instance is used as a session store for a web application. You need to ensure that session data is not lost during a node failure. What should you do?

Accepted Answer

Enable AOF persistence in the Memorystore instance.. Memorystore for Redis supports persistence via RDB snapshotting or AOF (Append-Only File). For minimal data loss during a node failure, AOF persistence is recommended because it logs every write operation, allowing recovery with only a few seconds of data loss (depending on fsync settings). Standard Tier with replication provides high availability but does not persist data to disk, so a full zone failure can cause data loss. Periodic exports to Cloud Storage have gaps between exports, leading to data loss of up to the export interval. Therefore, enabling AOF persistence is the best approach to prevent data loss during a node failure.

Answer

Use a Basic Tier instance with a large maxmemory setting.

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Configure the instance as Standard Tier (with replication) and schedule periodic exports to Cloud Storage.

Answer

Enable persistence by setting the 'persistence' parameter to 'rdb' in the instance configuration.

Question 5

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).. Option A is correct because Memorystore for Redis supports vertical scaling, allowing you to increase the memory capacity of an existing instance or upgrade from Basic Tier to Standard Tier, which provides replication and higher availability to handle increased load. Option E is correct because enabling Redis Cluster mode on a Memorystore instance allows horizontal scaling by distributing data across multiple shards, increasing total capacity and throughput beyond a single instance's limits. Option B is not a native Memorystore scaling action; while client-side sharding is a general Redis pattern, Memorystore does not provide built-in support for managing multiple instances as a single sharded cluster this way. Option C is incorrect because changing the eviction policy to noeviction does not add memory or capacity; it only changes how Redis behaves when memory is full, and can cause write errors instead of scaling. Option D is incorrect because Memorystore for Redis read replicas are only available in Standard Tier and are used for read scaling and high availability, not for increasing write capacity or memory size, and the current instance is Basic Tier.

Answer

Create additional instances and implement client-side sharding.

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Change the eviction policy to noeviction to allow more data.

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Add read replicas to offload read traffic.

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 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 8

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.. Cloud Spanner's scheduled backups support a cross-region backup policy, allowing backups to be stored in a different region for compliance and restorable directly within Spanner without export/import. This satisfies the daily full backup, cross-region, and no-export/import requirements.

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 9

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 10

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

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disk_read_ops

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cpu_utilization