PCD Deploy Scalable and Highly Available Databases in Google Cloud — 20 Questions

Question 1

An engineer needs to create a Cloud SQL MySQL instance that can automatically failover to a standby in a different zone within the same region. Which configuration should be used?

Accepted Answer

Regional HA configuration. Cloud SQL HA configuration creates a primary and a standby instance in different zones within the same region. The standby is synchronously replicated and automatic failover occurs in under 60 seconds. Cross-region failover is not supported; read replicas are for read scaling and DR, not automatic failover. Zonal availability is a single-zone instance without HA.

Answer

Read replica in same zone

Answer

Zonal availability configuration

Answer

Cross-region failover replica

Question 2

A company runs a critical PostgreSQL database on Cloud SQL. They want to enforce that all client connections use SSL/TLS encryption. Which step is necessary to ensure this?

Accepted Answer

Set the 'require_ssl' flag to 'on' for the instance. Cloud SQL provides a server-side SSL certificate and optionally enforces encryption using the 'require_ssl' flag (or 'cloudsql.ssl_mode' in newer versions). IAM authentication does not enforce SSL. The Auth Proxy uses SSL by default but does not enforce it at the database level. Private IP alone does not encrypt traffic.

Answer

Enable IAM database authentication

Answer

Use the Cloud SQL Auth Proxy to connect

Answer

Assign a private IP address to the instance

Question 3

A company uses Cloud Spanner with an instance configured with 1000 processing units. They notice that high-priority CPU utilization consistently exceeds 65% during peak hours, causing increased latency. They want to auto-scale based on this metric. Which scaling configuration should they use?

Accepted Answer

Use autoscaling with a minimum of 1000 processing units, a maximum of 2000 processing units, and a target high-priority CPU utilization of 65%. Cloud Spanner autoscaling uses processing units (not nodes) and allows setting a target for high-priority CPU utilization. Setting a minimum of 1000 processing units ensures a baseline, and a maximum of 2000 allows scaling up. The target high-priority CPU utilization (e.g., 65%) triggers scaling. Node-based options are not used with processing units.

Answer

Use autoscaling with a minimum of 1000 processing units, a maximum of 2000 processing units, and a target CPU utilization of 65%

Answer

Use autoscaling with a minimum of 1 node, a maximum of 2 nodes, and a target CPU utilization of 65%

Answer

Manually increase processing units to 2000

Question 4

A company is migrating an on-premises Oracle database to Cloud SQL for PostgreSQL. They require a deployment that supports up to 30,000 transactions per second (TPS) and provides automatic storage scaling. Which instance configuration should they choose?

Accepted Answer

High-memory machine type with SSD and storage auto-increase enabled. Cloud SQL supports storage auto-increase regardless of machine type. For high TPS, a high-memory machine type (e.g., highmem) provides more memory per CPU, which can improve performance for database workloads. SSD is required for consistent performance. HDD is not recommended for production.

Answer

Standard machine type with HDD and storage auto-increase enabled

Answer

Custom machine type with 4 vCPUs and 15 GB memory, SSD, and storage auto-increase enabled

Answer

Lightweight machine type with SSD and storage auto-increase disabled

Question 5

An engineer is using Firestore Security Rules for a mobile app. They want to ensure that a user can only read their own documents, where each document has a field 'userId' matching the user's authenticated UID. Which rule is correct?

Accepted Answer

service cloud.firestore { match /databases/{database}/documents { match /{document=**} { allow read: if resource.data.userId == request.auth.uid; } } }. Firestore Security Rules use the `request.auth.uid` variable to get the authenticated user's UID and `resource.data.userId` to access the document field. The correct condition checks that the document's 'userId' equals the requester's UID. `request.resource` refers to incoming data, not existing data.

Answer

service cloud.firestore { match /databases/{database}/documents { match /{document=**} { allow read: if request.auth.uid == get(/databases/$(database)/documents/$(document)).data.userId; } } }

Answer

service cloud.firestore { match /databases/{database}/documents { match /{document=**} { allow read: if request.auth.uid == request.resource.data.userId; } } }

Answer

service cloud.firestore { match /databases/{database}/documents { match /{document=**} { allow read: if request.auth.uid == resource.data['user-id']; } } }

Question 6

A development team wants to test their application locally with Cloud Bigtable without incurring costs. Which instance type should they create?

Accepted Answer

Development instance. Cloud Bigtable offers a 'Development' instance type for testing and development. It uses a single node (or limited cluster) and costs significantly less than a production instance. Production instances are for live workloads. An HDD cluster is for production with slower storage. A multi-cluster is for replication.

Answer

Production instance with a single node

Answer

Production instance with a multi-cluster configuration

Answer

Production instance with HDD storage

Question 7

A company is deploying AlloyDB for PostgreSQL in multiple regions to support disaster recovery. They need the secondary region to be able to serve reads and automatically scale read capacity. Which configuration should they use?

Accepted Answer

Create a primary cluster in the primary region and a read pool cluster in the secondary region with autoscaling enabled on the read pool. AlloyDB supports cross-region replication using read pool instances in secondary regions. These read pools can have autoscaling enabled to automatically adjust the number of nodes based on load. Primary instances are for writes only. AlloyDB Omni is for on-premises, not cross-region replication. A single cluster with multiple read pools in the same region does not provide cross-region DR.

Answer

Create a primary cluster in the primary region and a primary cluster in the secondary region, then set up bidirectional replication

Answer

Use AlloyDB Omni in the secondary region to replicate data from the primary region

Answer

Create a primary cluster with multiple read pools in the same region and distribute read traffic

Question 8

A Cloud Spanner instance has been running with 2 nodes. The team wants to migrate to processing units for more granular scaling. What is the equivalent number of processing units for 2 nodes?

Accepted Answer

2000 processing units. In Cloud Spanner, 1 node equals 1000 processing units. Therefore, 2 nodes equal 2000 processing units. This conversion is standard, though the documentation may vary slightly (some sources say 1 node = 1000 PUs). 500 PUs would be half a node, and 4000 would be 4 nodes.

Answer

1000 processing units

Answer

4000 processing units

Answer

500 processing units

Question 9

An engineer is monitoring Cloud Bigtable performance and notices high read latency. They suspect a hot spot issue. Which tool should they use to identify the hot spot?

Accepted Answer

Key Visualiser. Cloud Bigtable's Key Visualiser is a tool specifically designed to detect and visualize hot spots (uneven distribution of read/write load across row keys). It helps identify row key patterns causing performance issues. Stackdriver is the legacy name for Cloud Monitoring; Cloud Monitoring can show overall metrics but not hot spot analysis. Bigtable Studio does not exist. cbt is the CLI tool.

Answer

The cbt command-line tool

Answer

Bigtable Studio

Answer

Cloud Monitoring (formerly Stackdriver)

Question 10

A company wants to connect to Cloud SQL from a Compute Engine VM without exposing the database to the public internet. They also need to avoid IP allowlisting. Which connection method should they use?

Accepted Answer

Use the Cloud SQL Auth Proxy. The Cloud SQL Auth Proxy securely connects to Cloud SQL using private IP without requiring IP allowlisting. It uses IAM permissions for authentication. Direct IP connection with SSL still requires IP allowlisting. Using only private IP does not provide secure authentication by itself; the Auth Proxy adds IAM-based authentication. The Cloud SQL Connector libraries are client-side libraries that offer similar functionality but are not a standalone connection method.

Answer

Assign a private IP to the Cloud SQL instance and connect using it

Answer

Use the Cloud SQL Connector library inside the VM

Answer

Use a direct IP connection with SSL enabled

Question 11

A company needs a fully managed, globally distributed relational database that supports ACID transactions across regions. Which Google Cloud service should they choose?

Accepted Answer

Cloud Spanner. Cloud Spanner is the only Google Cloud database that is fully managed, globally distributed, and supports ACID transactions. Cloud SQL is regional. Bigtable is NoSQL and does not support ACID transactions. Firestore is a document database with limited transaction support but not globally distributed in the same way.

Answer

Firestore

Answer

Cloud Bigtable

Answer

Cloud SQL

Question 12

An engineer needs to create a cross-region read replica for a Cloud SQL for MySQL instance for disaster recovery. Which step is required?

Accepted Answer

Create the replica in a different region. Cross-region read replicas are supported in Cloud SQL for MySQL. The engineer can create a read replica in a different region from the primary instance. Read replicas are promoted for DR. HA configuration is regional only. External replicas are for on-premises. Binary logging must be enabled on the primary.

Answer

Create the replica in a different zone within the same region

Answer

Configure an external replica in the target region

Answer

Enable HA on the primary instance first

Question 13

A company is deploying a production Cloud Bigtable instance for time-series data. They want high availability across zones and the ability to serve reads from a secondary location. Which TWO configurations should they implement?

Accepted Answer

Add a second cluster in a different zone within the same region. To achieve high availability across zones, you add a second cluster in a different zone within the same region. For read scaling or cross-region DR, you can add a cluster in another region. A production instance is required for multi-cluster. Replication is asynchronous, so eventual consistency. A development instance does not support multiple clusters.

Answer

Create a development instance type

Answer

Disable replication to avoid conflicts

Answer

Use HDD storage to reduce costs

Question 14

An engineer is designing a Cloud Spanner instance for a global e-commerce application. They need strong consistency across continents and the ability to automatically scale compute capacity. Which THREE configurations should they choose?

Accepted Answer

Enable autoscaling with processing units and set min and max. For global strong consistency, a multi-region configuration is required (e.g., nam3, eur3). To auto-scale, you use processing units with a min and max, and set a target high-priority CPU utilization. Nodes are not used with autoscaling. Regional configurations only cover one region. Single-region does not provide global consistency.

Answer

Use nodes with a fixed number

Answer

Use a regional configuration

Question 15

A company uses Firestore for a mobile app. They want to implement security rules that allow users to create documents only if they are authenticated and the document's 'owner' field matches their UID. Additionally, they want to allow reads of any document where the 'visibility' field is 'public'. Which TWO conditions should the rules include?

Accepted Answer

allow read: if resource.data.visibility == 'public';. The create rule should check authentication and that the incoming document's owner matches the UID. The read rule should allow if visibility is public. Using get() for the existing document is not needed for create because request.resource refers to the new document. For read, resource.data refers to the existing document.

Answer

allow create: if resource.data.owner == request.auth.uid;

Answer

allow read: if request.resource.data.visibility == 'public';

Answer

allow write: if request.auth.uid != null;

Question 16

A company is migrating a PostgreSQL application to Cloud SQL. They require automatic failover in under 60 seconds if the primary instance fails, and they want to minimize write latency. Which configuration should they choose?

Accepted Answer

Create a Cloud SQL for PostgreSQL instance with high availability (HA) configuration.. Cloud SQL HA uses a synchronous standby in a different zone within the same region, providing automatic failover in under 60 seconds and no data loss. Cross-region replicas are asynchronous and do not meet the failover time requirement. Zonal instances lack HA. Regional clusters are for Spanner.

Answer

Create a zonal Cloud SQL instance and set up a read replica in a different zone.

Answer

Create a Cloud SQL for PostgreSQL instance with cross-region replication.

Answer

Configure a Cloud Spanner regional instance with multi-zone nodes.

Question 17

A financial services company needs a globally distributed, strongly consistent database that can handle OLTP workloads with high throughput and automatic scaling. Which Google Cloud database should they use?

Accepted Answer

Cloud Spanner. Cloud Spanner is the only Google Cloud database that provides global distribution with strong consistency and horizontal scaling for OLTP workloads. Bigtable is eventually consistent across regions. Cloud SQL is regional. Firestore is eventually consistent and limited to single-region or limited multi-region.

Answer

Firestore

Answer

Cloud SQL

Answer

Cloud Bigtable

Question 18

An engineering team is designing an AlloyDB cluster for an e-commerce platform. They anticipate variable read traffic and want to automatically add or remove read-only compute capacity based on CPU utilization. Which feature should they enable?

Accepted Answer

Read pool autoscaling. AlloyDB’s read pool autoscaling automatically adjusts the number of read pool instances based on metrics like CPU utilization. Query distribution is built-in, but autoscaling is the specific feature for capacity changes. Instance groups are a Compute Engine concept. Read replicas in Cloud SQL are not automatically scaled.

Answer

Enable query distribution across read pool instances.

Answer

Configure a managed instance group for the read pool.

Answer

Set up Cloud SQL read replicas with cross-region replication.

Question 19

A developer needs to connect a Cloud SQL MySQL instance from an application running on Compute Engine without whitelisting IP addresses. Which method should they use?

Accepted Answer

Configure the application to use Cloud SQL Auth Proxy.. Cloud SQL Auth Proxy provides secure access using IAM permissions, avoiding the need to whitelist IP addresses. SSL without proxy still requires IP allowlisting. Private IP requires VPC peering and is not automatically connected. Cloud Shell is not for application connectivity.

Answer

Connect via Cloud Shell using the mysql client.

Answer

Set up a Cloud SQL private IP connection.

Answer

Use SSL/TLS connection with the public IP address.

Question 20

A company uses Cloud Bigtable for time-series data. They notice uneven load distribution across nodes causing hot spots. Which tool should they use to identify the hot spots?

Accepted Answer

Cloud Bigtable Key Visualiser. Cloud Bigtable Key Visualiser graphically shows read/write heatmaps to identify hot spots. Monitoring dashboards show metrics but not specific hot spots. cbt tool is CLI, not visual. Cloud Logging records operations but doesn't visualize load distribution.

Answer

Cloud Monitoring dashboards

Answer

cbt command-line tool

Answer

Cloud Logging