PCDE Practice Exam 60 — 20 Questions

Question 1

You are configuring a dashboard-as-code using the Cloud Monitoring API. You want to create a dashboard that shows a heatmap of request latency distribution across all services. Which chart type and aggregation should you use?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Heatmap chart using a distribution metric. Heatmaps in Cloud Monitoring are created using a 'heatmap' chart type, which displays the distribution of metric values over time. This requires a distribution metric (e.g., from OpenTelemetry or custom) that records a histogram. The heatmap visualizes percentiles or count per bucket over time. Line, stacked bar, and scorecard cannot show distribution.

Answer

Stacked bar chart with mean aggregation

Answer

Line chart with 95th percentile aggregation

Answer

Scorecard chart with MAX aggregation

Question 2

An organization is migrating from Teradata to BigQuery. They have 20 TB of data, complex BTEQ scripts, and require near-zero downtime. Which THREE components should be part of their migration plan? (Choose THREE.)

Accepted Answer

Schema Conversion Tool (SCTS). Schema Conversion Tool (SCTS) is correct because it automates the conversion of Teradata-specific DDL, BTEQ scripts, and stored procedures into BigQuery-compatible SQL. This is critical for migrating 20 TB of data and complex BTEQ scripts without manual rewriting, reducing errors and accelerating the migration timeline.

Answer

Cloud SQL Auth Proxy

Answer

Database Migration Service (DMS)

Question 3

The exhibit shows IAM policy for a BigQuery dataset. The BI team reports they can query tables but cannot create views. What is the missing role?

Accepted Answer

roles/bigquery.dataEditor. The BI team can query tables but cannot create views, which requires write access to the dataset. The `roles/bigquery.dataEditor` role grants permissions to read, create, update, and delete datasets, tables, and views, including the `bigquery.tables.create` and `bigquery.tables.update` permissions necessary for view creation. The existing query capability indicates they have at least `roles/bigquery.dataViewer`, but view creation demands the additional write permissions provided by `dataEditor`.

Answer

roles/bigquery.admin

Answer

roles/bigquery.metadataViewer

Answer

roles/bigquery.user

Question 4

You are a Cloud Database Engineer managing a Cloud Spanner instance. You notice that some queries are taking longer than expected. You suspect that the queries are not using secondary indexes efficiently. Which TWO metrics should you monitor in Cloud Monitoring to validate your suspicion? (Choose two.)

Accepted Answer

Statement scan rows returned. 'Statement scan rows returned' measures the number of rows scanned by a query, which directly indicates whether a full table scan is occurring instead of an efficient index seek. If this metric is high relative to the rows returned, it confirms that secondary indexes are not being used effectively, leading to longer query times.

Answer

CPU utilization

Answer

Lock conflicts

Answer

Query scan latency (mean)

Question 5

A team uses Cloud Run for a web application that experiences sporadic traffic. They want to minimize cold starts without incurring costs when there are no requests. Which configuration should they use?

Accepted Answer

Set min instances to a value greater than 0. To minimize cold starts, the service needs at least one warm instance ready to handle requests, which requires setting min instances to a value greater than 0. While this incurs costs even when there are no requests (since instances remain allocated), it eliminates the latency of cold starts. Setting min instances to 0 would reduce costs to zero during idle periods, but it would cause cold starts on every request ramp-up, contradicting the goal of minimizing cold starts. The requirement to 'not incur costs when there are no requests' is inherently conflicting with minimizing cold starts; the best compromise under the stated goals is to set min instances > 0.

Answer

Set min instances to 0

Answer

Set CPU always-on to true

Answer

Set concurrency to 1000

Question 6

A financial services firm needs a database for real-time fraud detection that requires single-digit millisecond latency for lookups on a precomputed feature set. The dataset is 5 TB and grows by 1 TB per month. Which database service BEST meets these requirements?

Accepted Answer

Cloud Bigtable. Bigtable is designed for high-throughput, low-latency access to large datasets. It can handle 5 TB (or more) with SSD nodes. Cloud SQL and Spanner have lower throughput limits. BigQuery is not real-time.

Answer

BigQuery

Answer

Cloud Spanner

Answer

Cloud SQL (MySQL)

Question 7

A team uses Cloud Deploy to manage deployments to GKE. They want to automatically roll back to the previous revision if a canary deployment fails health checks. What should they configure?

Accepted Answer

Set 'rollback-on-failure: true' in the delivery pipeline definition. Cloud Deploy supports automatic rollback on failure for canary deployments by setting `rollback-on-failure: true` in the delivery pipeline definition. When a canary deployment fails health checks, Cloud Deploy automatically reverts to the previous stable revision without manual intervention, ensuring minimal downtime and consistent release governance.

Answer

Configure a manual approval gate before promotion

Answer

Set the deployment strategy to blue/green

Answer

Use a Cloud Build step to run kubectl rollout undo

Question 8

After promoting a Cloud SQL destination in a DMS continuous migration, the application team updates the connection strings. However, they want a rollback plan in case issues arise. What should they keep running to allow a rollback?

Accepted Answer

Keep the source database running in read-only mode. Keeping the source database running (read-only) allows reverting to it if needed. The DMS job is stopped after promotion. The destination is now the primary. Keeping both writable could cause conflicts.

Answer

Keep both databases writable

Answer

Keep the destination database in read-only mode

Answer

Keep the DMS job active

Question 9

A financial firm uses Cloud Spanner with a single-region configuration. They must meet regulatory requirements for disaster recovery across continents. They need to recover within 1 hour RTO and RPO of 5 minutes. Current workload: 50k writes/sec. What should they do?

Accepted Answer

Use multi-region configuration with synchronous replication across two continents.. Cloud Spanner's multi-region configuration uses synchronous replication across continents, providing strong consistency and automatic failover. This meets the 1-hour RTO and 5-minute RPO requirements for disaster recovery, as synchronous replication ensures data is durable across regions with minimal lag, and Spanner handles failover transparently without manual intervention.

Answer

Use cross-region backups with 5-minute retention.

Answer

Use Cloud SQL for MySQL with cross-region replicas.

Answer

Use export to Cloud Storage every 5 minutes.

Question 10

You need to design a Cloud Bigtable row key for a time-series application that records user activity. The most common queries filter by user_id and then by timestamp (most recent first). Which row key design is MOST appropriate?

Accepted Answer

user_id#reverse_timestamp. For time-series with frequent queries filtering by user_id and recent data, the recommended design is to put user_id first and then use a reverse timestamp. This ensures data for a user is co-located and the latest data appears first when scanning.

Answer

user_id#timestamp

Answer

reverse_timestamp#user_id

Answer

timestamp#user_id

Question 11

An organization is using Cloud SQL for MySQL with automated backups enabled. They need to restore a backup to a new instance in a different region for testing. The backup is stored in the same region as the source. How can they achieve this with minimal operational overhead?

Accepted Answer

Restore the backup to a new instance in the same region, then use export/import to move data to the target region.. Cloud SQL backups are region-specific and cannot be restored directly to a different region. The minimal-operational-overhead approach is to restore the backup to a new instance in the same region, then use the export/import feature (e.g., SQL dump or CSV) to move the data to the target region. This avoids the complexity and cost of maintaining a cross-region read replica, while still achieving the goal with built-in tools.

Answer

Use gcloud sql backups restore with the --restore-instance flag pointing to a new instance in the target region.

Answer

Create a cross-region read replica from the source, then promote it in the target region.

Answer

Restore the backup directly to a new instance in the target region using the Cloud Console.

Question 12

A Memorystore for Redis instance needs to be scaled to handle increased traffic. Which TWO methods can you use? (Choose 2)

Accepted Answer

Vertically scale by changing the tier to a larger machine type.

Answer

Increase the maxmemory parameter.

Answer

Change the eviction policy to allkeys-lru.

Answer

Add read replicas in the same zone.

Question 13

A game company uses Cloud Bigtable to store player session data. Access patterns include looking up a player's most recent sessions and scanning sessions by time range. Which row key design is most appropriate?

Accepted Answer

Use a row key of player ID followed by reversed timestamp.. It leverages Cloud Bigtable's sorted row key structure to group all sessions for a given player ID together, while the reversed timestamp ensures that the most recent session appears first within that group. This design enables efficient point lookups for a player's latest sessions and supports range scans over time ranges by using the timestamp portion of the key.

Answer

Use only player ID as row key with column qualifiers for timestamps.

Answer

Prefix with timestamp and append player ID.

Answer

Use a hash of player ID as row key and store timestamps in cell versions.

Question 14

Refer to the exhibit. You receive the following query output showing bytes processed for a BigQuery query. The table is partitioned by date and clustered on country. What is the most likely reason for the high bytes processed?

Accepted Answer

The query does not filter on the clustering column, causing full scan of selected partitions. BigQuery clustering only reduces the bytes scanned when the query filters on the clustering column (country). Without a WHERE clause on country, BigQuery must scan all rows in the selected partitions, even though partition pruning may reduce the date range. The high bytes processed indicates that clustering is not being leveraged, so the query performs a full scan of the chosen partitions.

Answer

The GROUP BY country requires sorting all rows

Answer

The table is not partitioned correctly

Answer

The date range is too wide

Question 15

A team is designing a Cloud Spanner schema for a global social media application. The table 'Posts' has a primary key of (UserId, PostId) where PostId is a UUID. They notice write hotspots on the server with monotonically increasing UserId values. What is the most effective schema design change to distribute writes evenly?

Accepted Answer

Add a hash prefix to the UserId to create a composite primary key like (HashUserId, UserId, PostId). Using a hash prefix on the first part of the primary key (e.g., hash of UserId) helps distribute writes across splits, avoiding hotspots. Using a UUID for PostId is good but UserId ordering still causes hotspots. Adding a timestamp as a second part doesn't help. Interleaving with User is fine but doesn't fix the hotspot issue.

Answer

Create a secondary index on PostId

Answer

Place PostId first in the primary key

Answer

Use a monotonically increasing integer for PostId instead of UUID

Question 16

Refer to the exhibit. A developer creates these tables and notices that queries joining Users and Orders on UserId are slow. What is the most likely cause?

Accepted Answer

Tables are not interleaved, so parent and child rows may be in different splits.. In Google Cloud Spanner, interleaving tables physically co-locates parent and child rows in the same tablet split, reducing cross-node lookups. Without interleaving, rows from Users and Orders may reside on different servers, causing distributed queries that are slower due to network round trips. Option C correctly identifies this as the most likely cause of slow joins.

Answer

The primary key of Orders should include UserId as a prefix for co-location.

Answer

The foreign key constraint is missing, causing full table scans.

Answer

The foreign key reference should be on the parent table.

Question 17

An organization needs a multi-region database deployment with strong consistency and an RPO of zero in normal operation. They expect a regional outage and require automatic failover within seconds. Which database service and configuration meets these requirements?

Accepted Answer

Cloud Spanner multi-region configuration. Cloud Spanner multi-region configurations provide strong consistency, zero RPO during normal operation, and automatic failover within <1 minute (typically seconds) in case of regional failure.

Answer

Cloud Firestore in multi-region mode

Answer

Cloud Bigtable with multi-cluster routing and replication

Answer

Cloud SQL with cross-region read replica

Question 18

A global retail company uses Cloud Spanner to manage product inventory. They need to apply a schema change to add a new column to a table that has 10 billion rows. Which THREE strategies should they consider to minimize downtime?

Accepted Answer

Schedule the schema change during a period of low traffic.. Scheduling schema changes during low traffic reduces the risk of contention and performance impact on the live database. Cloud Spanner applies schema changes online without locking the entire table, but heavy write traffic can still cause transaction conflicts or increased latency; performing the change during a quiet period minimizes these risks.

Answer

Disable the table, add the column, then re-enable.

Answer

Create a new table with the column, then copy data in batches.

Question 19

A Cloud SQL for PostgreSQL instance is used for an OLTP application. The database schema has many foreign key constraints. Which action improves write performance?

Accepted Answer

Create indexes on foreign key columns.. Creating indexes on foreign key columns prevents full table scans when checking referential integrity, reducing lock contention and improving write performance. Option B is wrong because dropping foreign key constraints sacrifices data integrity, but it could actually improve write performance; however, this is not a best practice and violates data consistency. Option C is wrong because adding triggers adds overhead to write operations, slowing performance. Option D is wrong because increasing storage size does not address the performance bottleneck caused by missing indexes on foreign key columns.

Answer

Drop all foreign key constraints.

Answer

Add more triggers to enforce integrity.

Answer

Increase the instance storage size.

Question 20

A company is migrating its on-premises PostgreSQL database to Cloud SQL for PostgreSQL. They want to minimize downtime during the migration. Which TWO actions should they take?

Accepted Answer

Set up a Cloud SQL read replica and promote it to the primary after migration.. Setting up a Cloud SQL read replica from the source PostgreSQL database and then promoting it to primary allows for a controlled cutover with minimal downtime. The replica stays in sync with the source using PostgreSQL's native streaming replication, and promotion is a fast metadata operation that typically takes seconds, not minutes or hours.

Answer

Increase the disk size of the Cloud SQL instance before migration to improve performance.

Answer

Use pg_dump to export the database and pg_restore to import into Cloud SQL.

Answer

Decrease max_connections to reduce load during migration.