PCDE Manage a solution that can span multiple database technologies Practice Test 4 — 15 Questions

Question 1

A DevOps engineer needs to monitor Cloud SQL for MySQL replication lag on a read replica to ensure data freshness. Which Cloud Monitoring metric should they create an alert on?

Accepted Answer

cloudsql.googleapis.com/database/replication/lag. The Cloud Monitoring metric cloudsql.googleapis.com/database/replication/lag is the correct metric for monitoring replication lag on a Cloud SQL for MySQL read replica. It reports the delay between the primary and replica, which is exactly what the DevOps engineer needs to alert on for data freshness.

Answer

cloudsql.googleapis.com/database/replica/state

Answer

cloudsql.googleapis.com/database/postgresql/replication/lag

Answer

cloudsql.googleapis.com/database/mysql/replication/seconds_behind_master

Question 2

A large enterprise uses Cloud Bigtable for analytics. They notice that some nodes are handling significantly more traffic than others, causing hot spots and performance degradation. Which tool should they use to identify the specific row keys causing the issue?

Accepted Answer

Bigtable Key Visualiser. Key Visualiser is a Bigtable tool that provides a heatmap of row key access patterns, helping to identify hot spots by showing which row key ranges are heavily accessed.

Answer

Stackdriver Error Reporting

Answer

Bigtable cbt tool with read rows command

Answer

Cloud Monitoring dashboard for Bigtable

Question 3

A developer is setting up a Memorystore for Redis instance and needs to restrict access to only a specific Compute Engine VM in the same VPC network. Which configuration should they use?

Accepted Answer

Configure the Memorystore instance with a firewall rule that allows only the VM's internal IP. Memorystore for Redis instances are reachable only over private IPs inside the VPC, so access control is enforced with VPC firewall rules. Creating an ingress rule that permits only the specific Compute Engine VM's internal IP on the Redis port restricts connectivity to that VM. This is the standard, supported method for scoping Memorystore access to a single client.

Answer

Use Cloud Armor to whitelist the VM's external IP

Answer

Use the AUTH password and share it only with the VM

Answer

Place the Redis instance in a separate VPC and peer only with the VM's VPC

Question 4

A company runs a Memorystore for Redis cluster with standard tier (for replication). They need to ensure high durability of session data and be able to recover from a complete zone failure. Which three actions should they take? (Choose THREE.)

Accepted Answer

Schedule regular exports of the instance data to Cloud Storage using gcloud. To ensure high durability and recovery from a complete zone failure for a Memorystore for Redis cluster with standard tier (replication enabled): Option A: Regular exports to Cloud Storage provide point-in-time backups that can be restored in a different zone if needed. Option B: Cross-region replication creates a replica in another region, allowing failover if the primary zone fails. Option E: Setting up a second instance in a different zone with client-side replication allows the application to switch to the replica if the primary zone fails. Option C is incorrect because Redis Cluster with multiple shards is for horizontal scaling and does not inherently provide zone failure recovery or durability beyond what replication provides. Option D is incorrect because RDB persistence, while supported in Memorystore for Redis, only provides local recovery and does not protect against a complete zone failure; you need cross-zone or cross-region replication for that.

Answer

Use a Redis Cluster with multiple shards for horizontal scaling

Answer

Enable RDB persistence on the primary instance

Question 5

A company wants to migrate from an on-premises MySQL database to Cloud SQL. They need to minimize downtime and ensure data consistency. Which two steps should they include in the migration plan? (Choose TWO.)

Accepted Answer

Set up continuous replication from the on-premises database to the Cloud SQL instance using Database Migration Service. Database Migration Service (DMS) supports continuous replication using MySQL binary logs, enabling a near-zero-downtime migration by keeping the Cloud SQL instance synchronized with the on-premises database until cutover. Option D is correct because taking a consistent snapshot (e.g., using mysqldump with --single-transaction or a storage-level snapshot) at cutover ensures data consistency and provides a fallback point if the migration fails.

Answer

Create a read replica in the same region for validation before cutover

Answer

Use Cloud SQL's import functionality to load a mysqldump file

Answer

Disable binary logging on the on-premises database to reduce overhead

Question 6

A Cloud SQL for MySQL instance's storage utilization has reached 95%. The database is 5 TB and needs to grow. The operations team tries to increase storage via gcloud but receives an error. What is the likely cause?

Accepted Answer

The instance is at the maximum storage limit for its machine tier. Cloud SQL for MySQL enforces a maximum storage limit that depends on the machine tier (vCPU/memory) of the instance. When an instance is already at that tier's ceiling, attempts to increase storage via gcloud fail with an error indicating the limit has been reached. The fix is typically to increase the machine tier first, then grow storage.

Answer

The storage resize operation is only allowed during maintenance windows

Answer

The instance has binary logging enabled, which prevents storage increase

Answer

The instance has automatic storage increase disabled

Question 7

A Memorystore for Redis instance is running out of memory. The application uses a mix of cache and session data. Which eviction policy should be chosen to minimize cache misses while ensuring session data is not evicted?

Accepted Answer

volatile-ttl. The volatile-ttl policy evicts keys with a TTL set, prioritizing those with the shortest remaining TTL. Since session data typically has a TTL and cache data may or may not, this policy allows you to protect session data by assigning it a longer TTL, while cache data with shorter TTLs is evicted first, minimizing cache misses.

Answer

noeviction

Answer

allkeys-lru

Answer

allkeys-random

Question 8

A company wants to monitor Cloud SQL database latency for read replicas and set up an alert if the replica lag exceeds 30 seconds. Which metric should be used?

Accepted Answer

cloudsql.googleapis.com/database/replication/replication_lag. The metric cloudsql.googleapis.com/database/replication/replication_lag measures the delay between the primary and read replica in Cloud SQL, expressed in seconds. It is the correct metric to monitor replica lag and trigger an alert when lag exceeds 30 seconds. This metric is available for both MySQL and PostgreSQL Cloud SQL instances with read replicas.

Answer

cloudsql.googleapis.com/database/postgresql/num_backends

Answer

cloudsql.googleapis.com/database/cpu/utilization

Answer

cloudsql.googleapis.com/database/disk/bytes_used

Question 9

A company is designing a disaster recovery plan for Cloud SQL for MySQL. They need to ensure the database can be recovered with minimal data loss (RPO of minutes) in case of a regional outage. Which TWO actions should they take?

Accepted Answer

Create a cross-region read replica. Option A (Create a cross-region read replica) is correct because a cross-region replica maintains a continuously updated copy of the primary in a different region, so during a regional outage it can be promoted to a standalone primary with only seconds-to-minutes of replication lag, satisfying the RPO of minutes. Option C (Enable binary logging with a PITR retention period) is correct because binary logging enables point-in-time recovery, allowing the instance to be restored to a specific timestamp (typically within the last 7 days by default) and thus recover data with minimal loss after an incident. Option B is not correct because a same-region read replica would be lost along with the primary during a regional outage, so it does not address regional disaster recovery. Option D is not correct because automatic storage increase only prevents out-of-disk failures and has no bearing on RPO or regional recovery. Option E is not correct because automated daily backups alone yield an RPO of up to 24 hours, which does not meet the requirement of minutes.

Answer

Set up a same-region read replica

Answer

Enable automatic storage increase

Answer

Configure automated daily backups

Question 10

A company uses Cloud SQL for PostgreSQL and needs to enable point-in-time recovery (PITR) with a retention period of 14 days. Currently, automated backups are configured with a 7-day retention. What should the engineer do to meet this requirement?

Accepted Answer

Note that Cloud SQL for PostgreSQL only supports up to 7 days of PITR retention; consider exporting logs to Cloud Storage for longer recovery.. Cloud SQL PITR is based on write-ahead log (WAL) archiving. The transaction log retention is set via the 'transaction log retention' setting, not the backup retention. PITR for PostgreSQL in Cloud SQL supports up to 7 days of log retention; 14 days is not supported. The engineer must accept the limitation or use a different approach.

Answer

Increase the backup retention period to 14 days; PITR is automatically extended.

Answer

Set the 'transaction log retention' to 14 days in the Cloud SQL instance settings.

Answer

Enable binary logging and set the binary log retention to 14 days.

Question 11

A Cloud Spanner database has a table 'Orders' with a column 'status'. The development team needs to add a new column 'priority INT64' to the table without downtime. Which statement should the database administrator execute?

Accepted Answer

ALTER TABLE Orders ADD COLUMN priority INT64;. Spanner supports online schema changes that are non-blocking. ALTER TABLE ... ADD COLUMN is the correct DDL statement and executes without locking the table.

Answer

CREATE INDEX idx_priority ON Orders (priority);

Answer

UPDATE Orders SET priority = 0; (no prior column)

Answer

ALTER TABLE Orders ADD priority INT64 NOT NULL DEFAULT 0;

Question 12

A company is using Memorystore for Redis and wants to ensure data persistence in case of a failure. What is the recommended approach?

Accepted Answer

Use Cloud Storage snapshots (export) or configure cross-region replication.. Memorystore for Redis does not provide built-in RDB or AOF persistence controls; the supported approach for durability is to export data to Cloud Storage (snapshots) or use cross-region replication for redundancy. This is the documented recommended pattern for persistence in Memorystore.

Answer

Configure a standard tier instance, which provides automatic persistence.

Answer

Enable RDB persistence and configure the backup interval.

Answer

Enable AOF persistence in Memorystore settings.

Question 13

A Cloud Bigtable instance is experiencing high latency on reads. The operations team suspects a hot spot. Which tool should they use to identify the hot spot?

Accepted Answer

Key Visualiser. Key Visualizer is the correct tool because it is specifically designed to visualize access patterns in Cloud Bigtable and identify hot spots—regions of a table that receive disproportionate read/write traffic. It generates heatmaps of row key access, allowing operators to pinpoint uneven load distribution that causes high latency.

Answer

Stackdriver Debugger

Answer

Bigtable cbt tool

Answer

Cloud Monitoring dashboard

Question 14

A team is using Firestore in Native mode. They have a collection 'users' with an array field 'roles'. They need to query all users where roles contains 'admin'. What index configuration is required?

Accepted Answer

Create an index exemption on the 'roles' field.. Firestore supports array membership queries using the 'array-contains' operator. An index exemption for the array field is required because Firestore does not automatically index array fields for array-contains queries. The exemption is created manually.

Answer

Create a single-field index on roles with ascending order.

Answer

Create a composite index on roles and the default field.

Answer

No index is needed; Firestore automatically supports array-contains queries.

Question 15

A company uses Cloud SQL for PostgreSQL. They need to monitor the replication lag on a read replica. Which metric should they use in Cloud Monitoring?

Accepted Answer

cloudsql.googleapis.com/database/postgresql/replication/replica_lag. The correct metric is cloudsql.googleapis.com/database/postgresql/replication/replica_lag because Cloud SQL for PostgreSQL exposes replication lag under a PostgreSQL-specific metric path. This metric reports the replication delay in seconds (or bytes, depending on the replica type) and is the standard way to monitor read replica lag for PostgreSQL instances. The other options either omit the database engine namespace or use incorrect metric names that do not exist in Cloud Monitoring.

Answer

cloudsql.googleapis.com/database/replication/replica_lag

Answer

cloudsql.googleapis.com/database/replication/lag_seconds

Answer

cloudsql.googleapis.com/database/postgresql/replication/lag