PCDE Practice Test 14 — 15 Questions

Question 1

An organization wants to restrict the creation of Compute Engine instances in their Google Cloud organization to only certain regions. Which organization policy constraint should they use?

Accepted Answer

constraints/gcp.resourceLocations. The organization policy constraint constraints/gcp.resourceLocations restricts where resources can be created by defining an allowed (or denied) list of locations (regions/zones) at the organization, folder, or project level. Applying it with an allow-list of specific regions prevents Compute Engine instances from being provisioned outside those regions. This is the canonical GCP control for geographic resource placement and data residency requirements.

Answer

compute.requireShieldedVm

Answer

constraints/compute.vmExternalIpAccess

Answer

iam.allowedPolicyMemberDomains

Question 2

A company uses Cloud SQL for MySQL and notices slow queries. They have enabled slow query logging and found that some queries are performing full table scans. The table has millions of rows. What is the best immediate action to improve query performance?

Accepted Answer

Create an index on the columns used in the WHERE clause.. Creating an appropriate index can eliminate full table scans and drastically improve query performance for the identified slow queries.

Answer

Increase the instance memory to allow more caching.

Answer

Use `EXPLAIN ANALYZE` to rewrite the query.

Answer

Add a read replica to offload the queries.

Question 3

A Firestore database in Native mode has a collection with a composite index on fields (city, age). A new query filters on 'city == 'London' AND 'age > 30' ORDER BY 'name'. The query is slow and reads many documents. What should the engineer do?

Accepted Answer

Create a composite index on (city, age, name).. The query filters on `city == 'London'` and `age > 30`, then orders by `name`. For Firestore to efficiently satisfy both the equality and inequality filters combined with an `ORDER BY`, the composite index must include the fields in the correct order: equality fields first, then the inequality field, then the sort field. Option C provides the index `(city, age, name)`, which matches this pattern exactly, allowing Firestore to perform a targeted index scan without reading extra documents.

Answer

Remove the ORDER BY clause to improve performance.

Answer

Create a composite index on (city, name).

Answer

Create a single-field index on 'name'.

Question 4

A company is setting up a new Google Cloud organization. The DevOps team wants to enforce that all Compute Engine instances are created only in us-central1 or europe-west1. Which approach should they use?

Accepted Answer

Create an organization policy with constraint `resourceLocations` and set allowed values to `us-central1` and `europe-west1`.. The `resourceLocations` organization policy constraint is specifically designed to restrict the set of Google Cloud locations where resources can be created. By setting allowed values to `us-central1` and `europe-west1`, the DevOps team enforces that Compute Engine instances (and other supported resources) can only be provisioned in those regions. This policy is evaluated at resource creation time and applies across the entire organization, project, or folder hierarchy.

Answer

Set a IAM policy on the organization to allow Compute Engine instances only in those regions.

Answer

Configure a VPC Service Controls perimeter to restrict resource creation to allowed regions.

Answer

Use Cloud Deployment Manager to enforce regions via a template that validates location.

Question 5

Your Cloud SQL for MySQL instance is experiencing intermittent performance degradation. You suspect that the issue is due to a sudden spike in connections from a specific application. Which metric and monitoring approach would best help you correlate the connection spike with performance degradation?

Accepted Answer

Monitor 'cloudsql.googleapis.com/database/mysql/threads/threads_connected' and correlate with CPU utilization and query latency.. The 'threads_connected' metric directly measures the number of active connections to the MySQL instance. Correlating this with CPU utilization and query latency allows you to pinpoint whether a sudden spike in connections is causing resource contention and degraded query performance, which is the exact scenario described.

Answer

Monitor 'cloudsql.googleapis.com/network/received_bytes_count' and compare with connection count.

Answer

Monitor 'cloudsql.googleapis.com/database/mysql/replication/seconds_behind_master' and compare with query latency.

Answer

Monitor 'cloudsql.googleapis.com/instance/uptime' and check for instance restarts during degradation.

Question 6

A company needs to ensure that their Cloud SQL for PostgreSQL instance can recover from a zonal failure within 60 seconds with minimal data loss. Which feature should they enable?

Accepted Answer

High availability (HA) configuration. Cloud SQL HA configuration automatically fails over to a standby instance in a different zone within the same region. This failover is automatic and typically completes in under 60 seconds, with near-zero data loss (synchronous replication). Cross-region replicas are manual and have longer RTO. Backups are not suitable for quick recovery.

Answer

Automated backups with PITR

Answer

Cross-region read replica

Answer

Enable deletion protection

Question 7

A company is designing a mobile application backend that requires real-time synchronization across users and offline support. Which Google Cloud database service is most suitable?

Accepted Answer

Firestore. Firestore is a serverless, NoSQL document database built for mobile and web apps, offering real-time listeners that push data changes to connected clients instantly and built-in offline persistence via local caching. These features directly satisfy the requirement for real-time synchronization across users plus offline support without custom sync code.

Answer

Bigtable

Answer

Cloud SQL

Answer

Cloud Spanner

Question 8

An e-commerce platform uses Cloud Bigtable for real-time user sessions. Write latency is high. On investigation, they find that rows are being written with monotonically increasing row keys (e.g., user_id + timestamp). What is the likely cause and solution?

Accepted Answer

Hotspotting on a single node; use salting or field promotion. Monotonically increasing row keys (e.g., user_id + timestamp) cause all writes to target a single tablet server, creating a hotspot. Cloud Bigtable distributes writes across nodes by row key range; sequential keys concentrate load on one node, degrading write latency. Salting (prepending a hash or random prefix) or field promotion (using a high-cardinality field as the first part of the key) spreads writes evenly across the cluster.

Answer

Too many column families; merge them

Answer

Inefficient reads; use reverse scan

Answer

Tablet splits are misconfigured; pre-split the table

Question 9

A company runs a Bigtable instance for time-series data. They need to reduce storage costs without compromising query performance for the most recent 30 days. Which two strategies should they implement?

Accepted Answer

Use Cloud Storage as a cold storage tier for historical data. Option B is correct because exporting historical time-series data to Cloud Storage (e.g., as Parquet/Avro files) moves cold data off Bigtable's SSD-backed storage, directly reducing the storage cost of the Bigtable instance while keeping the most recent 30 days in Bigtable for fast query performance. Option D is correct because configuring a garbage collection policy with an age-based rule (maxage=30d) automatically deletes cells older than 30 days, so Bigtable only stores and bills for the recent 30 days of data, which is exactly the retention window required. Option A is not appropriate because adding cluster nodes increases compute cost and does not reduce storage cost, and compaction is managed automatically by Bigtable. Option C is wrong because replication actually multiplies storage and compute costs across clusters, and deleting data from one cluster does not reduce the cost of the remaining cluster. Option E is wrong because reducing cluster nodes lowers compute capacity and can degrade performance, but it does not reduce the storage footprint of the data.

Answer

Increase the number of cluster nodes to improve compaction

Answer

Enable Bigtable replication and delete data from one cluster

Answer

Reduce the number of cluster nodes to save costs

Question 10

A company wants to migrate their on-premises PostgreSQL database to Cloud SQL. The database currently runs mixed workloads: OLTP with heavy writes and occasional complex analytical queries. They want to avoid performance impact on the transactional workload. Which approach should they take?

Accepted Answer

Create a read replica of the Cloud SQL instance and run analytical queries against the replica.. To avoid performance impact on transactional workloads, a read replica of the Cloud SQL instance should be created and analytical queries directed to it. Read replicas in Cloud SQL are separate instances that replicate data from the primary asynchronously, providing isolation so that heavy analytical queries don't compete for resources with OLTP operations. This is a recommended best practice for workload separation in Cloud SQL for PostgreSQL.

Answer

Migrate to Cloud Spanner to handle both workloads using its analytics interface.

Answer

Use Cloud SQL with the 'analytics' tier enabled.

Answer

Use the same Cloud SQL instance but schedule analytical queries during off-peak hours.

Question 11

Your Memorystore for Redis instance needs to survive a zonal failure with minimal data loss. Which feature should you use?

Accepted Answer

Use a Standard tier instance with replication across zones within the same region.. A Standard tier Memorystore for Redis instance with replication across zones provides automatic failover to a replica in a different zone, ensuring high availability and minimal data loss during a zonal failure. The Standard tier uses synchronous replication within the region, so data written to the primary is replicated to the cross-zone replica before acknowledging the write, which minimizes data loss to only in-flight transactions that were not yet committed.

Answer

Use a Basic tier instance and schedule periodic exports to Cloud Storage.

Answer

Enable persistence with RDB snapshots stored in Cloud Storage.

Answer

Create a cross-region replica (read replica in another region).

Question 12

Your team is migrating an on-premises PostgreSQL database to Cloud SQL for PostgreSQL. The current schema uses table inheritance, which is not fully supported in Cloud SQL. What should you do to minimize application changes?

Accepted Answer

Redesign the schema using separate tables with joins. Cloud SQL for PostgreSQL does not support table inheritance, a PostgreSQL-specific feature that allows child tables to inherit columns from a parent table. Option D is correct because redesigning the schema using separate tables with joins is the standard relational approach that works across all PostgreSQL deployments, including Cloud SQL, and minimizes application changes by preserving the logical data model.

Answer

Continue using inheritance as Cloud SQL supports it fully

Answer

Use PostgreSQL foreign data wrappers to emulate inheritance

Answer

Use materialized views to combine data

Question 13

A company is using Cloud Firestore to store user profiles. They need to query users by both their 'age' and 'city' fields. What must they configure to perform this query efficiently?

Accepted Answer

Create a composite index on age and city.. Firestore requires a composite index to efficiently execute queries that filter on multiple fields, such as age and city. Without a composite index, the query may fail or perform poorly because Firestore automatically indexes single fields but not combinations. Creating a composite index on age and city enables the query to be served efficiently.

Answer

Use Firestore in Datastore mode for automatic composite indexes.

Answer

Configure index exemptions for the fields.

Answer

No configuration needed; single-field indexes are sufficient.

Question 14

A database engineer is reviewing the configuration of a Cloud SQL for MySQL instance. The backup configuration shows binaryLogEnabled and pointInTimeRecoveryEnabled set to true. However, the engineer is unable to perform a point-in-time recovery (PITR) to a specific second within the last 30 days. What is the most likely reason?

Accepted Answer

The transaction log retention period is not set, defaulting to 7 days, so logs older than that are purged.. By default, Cloud SQL for MySQL sets the transaction log retention period to 7 days when binary logging and point-in-time recovery are enabled. This means that binary logs older than 7 days are automatically purged, making it impossible to perform a PITR to a specific second beyond that window, even if the backup retention is set to 30 days. To recover to any point within the last 30 days, the transaction log retention period must be explicitly configured to match the backup retention period.

Answer

Binary logging is not enabled for all databases on the instance.

Answer

The instance is not in a runnable state.

Answer

The database version is MySQL 8.0, which does not support PITR.

Question 15

A Cloud Bigtable cluster is currently using HDD storage. The team wants to switch to SSD for better performance. What is the correct approach?

Accepted Answer

Create a new cluster in the same instance with SSD, then delete the old HDD cluster.. In Cloud Bigtable, storage type is a property of the cluster, not the instance. You cannot change the storage type of an existing cluster. The correct approach is to add a new cluster with SSD storage to the same instance, then delete the original HDD cluster. This allows you to migrate without data loss or downtime, as data is replicated across clusters in the same instance.

Answer

Use the gcloud bigtable clusters update command with the --storage-type flag.

Answer

Export the table to Cloud Storage, delete the instance, create a new one with SSD, and import.

Answer

Delete the existing cluster and recreate it with SSD. Data is retained in the instance.