PCD Practice Test 28 — 15 Questions

Question 1

A Cloud SQL for MySQL instance configured with HA is experiencing a failover event. The application team reports that the database became unavailable for about 60 seconds during the failover. They want to minimize future downtime. What should they do?

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

Accepted Answer

Use Cloud SQL Proxy or configure the application to retry with a static IP. Cloud SQL HA failover typically takes less than 60 seconds. The downtime could be due to DNS propagation or connection pooling issues. Using a proxy like Cloud SQL Auth proxy or a load balancer with a static IP can reduce failover time by avoiding DNS changes.

Answer

Enable automated backups and point-in-time recovery

Answer

Increase the instance size to reduce failover time

Answer

Switch to a cross-region replica

Question 2

A financial services company needs a globally distributed database with strong consistency across continents, 99.999% SLA, and support for ACID transactions. They expect millions of transactions per day. Which Google Cloud database should they use?

Accepted Answer

Cloud Spanner. Cloud Spanner is the only Google Cloud database that offers global distribution with strong consistency, ACID transactions, and 99.999% SLA. It is designed for mission-critical workloads that require horizontal scaling and geo-replication.

Answer

Cloud SQL

Answer

Bigtable

Answer

Firestore

Question 3

A financial application requires ACID transactions across multiple rows and tables in a single region with less than 10ms latency and strong consistency. The application must handle up to 10,000 transactions per second. Which database should you use?

Accepted Answer

Cloud Spanner. Cloud Spanner provides ACID transactions, strong consistency, and horizontal scalability, with latency in the single-digit milliseconds for regional instances. It can handle 10K TPS easily. Cloud SQL is ACID but limited in scaling (read replicas, but not horizontal write scaling). Firestore is NoSQL with limited transaction scope. Bigtable is not ACID.

Answer

Cloud SQL

Answer

Firestore

Answer

Bigtable

Question 4

A developer is using Firestore in Native mode for a mobile app. They want to secure data access based on user authentication. Which TWO mechanisms should they use? (Choose two)

Accepted Answer

Firestore Security Rules. Firestore Security Rules allow granular access control. Firebase Authentication integrates with Firestore for user identity. IAM roles are for project-level access, not per-document. Cloud Armor is for network security. SSL/TLS is always enabled.

Answer

Cloud Armor

Answer

SSL/TLS encryption in transit

Answer

Cloud Identity and Access Management (IAM) roles

Question 5

A company needs to store petabytes of time-series IoT sensor data and query it with single-digit millisecond latency at millions of reads per second. The data has a simple key-value structure with timestamps. Which Google Cloud database is MOST appropriate?

Accepted Answer

Cloud Bigtable. Cloud Bigtable is designed for petabyte-scale, low-latency, high-throughput NoSQL storage for time-series, IoT, and financial data. It scales horizontally by adding nodes. BigQuery is for analytics (seconds-to-minutes latency), Cloud SQL for OLTP (limited throughput), Firestore for document data.

Answer

Firestore

Answer

BigQuery

Answer

Cloud Spanner

Question 6

You are designing a Cloud Spanner schema for a global user profile table with primary key UserId (UUID). Users frequently access their own profiles. Which index design minimizes read latency and avoids hotspotting?

Accepted Answer

Use a composite primary key with a hash prefix (e.g., INT64 hash of UserId) and UserId, and create a global secondary index on UserId with STORING clause. Using UUIDs as primary keys can cause hotspotting on the leading key. A better approach is to use a composite key with a sharding prefix (e.g., hash prefix) to distribute writes, and local indexes for single-region queries are not applicable. Global indexes with STORING clause avoid index joins and reduce read latency.

Answer

Use UUID as primary key and create a global index on UserId

Answer

Use UUID as primary key and rely on interleaved tables

Answer

Use a monotonically increasing integer as primary key

Question 7

A startup is building a mobile app with user-generated content (text and images). They need a database that provides offline support, real-time synchronization, and flexible security rules. Which TWO Google Cloud services should they consider? (Choose two)

Accepted Answer

Firestore. Firestore provides offline sync and real-time updates. Cloud Storage can store images and other large files with security rules. Cloud SQL and Bigtable are not suited for mobile offline sync.

Answer

Cloud SQL

Answer

Bigtable

Answer

Cloud Spanner

Question 8

A company runs a high-traffic web application that reads session data frequently. They want to reduce latency and offload database load. Which Google Cloud service should they use as a caching layer?

Accepted Answer

Memorystore for Redis. Memorystore (Redis) is the managed caching service on GCP, ideal for session stores and reducing database load. Cloud SQL, Bigtable, and Firestore are not suitable as low-latency caches.

Answer

Cloud SQL

Answer

Firestore

Answer

Cloud Bigtable

Question 9

Which Google Cloud database is serverless, supports offline data synchronization for mobile applications, and provides real-time updates via listeners?

Accepted Answer

Firestore. Firestore is a serverless NoSQL document database designed for mobile and web apps. It provides offline persistence, real-time listeners, and Security Rules for access control. Cloud SQL and Spanner are not serverless; Bigtable requires cluster management.

Answer

Cloud SQL

Answer

Cloud Spanner

Answer

Bigtable

Question 10

A global e-commerce platform requires a database that can handle millions of concurrent users, provide strong transactional consistency across regions, and achieve 99.999% availability SLA. Which database is the best fit?

Accepted Answer

Cloud Spanner. Cloud Spanner is the only Google Cloud database that offers global distribution, horizontal scaling, ACID transactions across regions, and a 99.999% SLA.

Answer

Cloud SQL with cross-region replication

Answer

Firestore in Native mode

Answer

Bigtable

Question 11

A developer is designing a Cloud Spanner schema for a blog application with tables: Posts (PostId, AuthorId, Title, Content) and Comments (CommentId, PostId, Author, Text). They want to store comments near their parent post for efficient retrieval. Which schema design should they use?

Accepted Answer

Use interleaving: define Comments as an interleaved table with Posts, with Comments primary key (PostId, CommentId). Interleaved tables in Cloud Spanner allow storing child rows (Comments) physically near parent rows (Posts) if the child table's primary key includes the parent's primary key. This improves locality and reduces cross-split reads.

Answer

Create a separate Comments table without interleaving and use application-level caching

Answer

Store comments as a JSON array within the Posts table

Answer

Use a foreign key from Comments to Posts and create a global secondary index on PostId

Question 12

An organization is migrating a MySQL database to Cloud SQL for MySQL. The source database uses the 'utf8' character set. To support emoji characters, what should they do before migration?

Accepted Answer

Change the character set to 'utf8mb4' on the source database before migration.. MySQL's 'utf8' character set does not support 4-byte Unicode characters like emojis. Cloud SQL for MySQL supports 'utf8mb4', which is the correct charset for full Unicode support.

Answer

No change needed; 'utf8' supports emoji in Cloud SQL.

Answer

Use 'latin1' character set instead for better performance.

Answer

Enable the 'character_set_emoji' flag in Cloud SQL.

Question 13

Which three of the following are managed database services offered by Google Cloud that support SQL or SQL-like query languages? (Choose 3)

Accepted Answer

AlloyDB. Cloud SQL, Cloud Spanner, and AlloyDB all support SQL. Bigtable uses HBase API, not SQL. Memorystore is a cache, not a database with SQL.

Answer

Memorystore

Answer

Cloud Bigtable

Question 14

A team is migrating a Teradata data warehouse to BigQuery. They need to assess the migration complexity. Which TWO factors are most critical in determining the level of effort for SQL translation?

Accepted Answer

Volume of BTEQ scripts and stored procedures that must be rewritten.. Teradata uses BTEQ scripts and has specific SQL syntax (e.g., QUALIFY, MACROS). The two critical factors are: 1) The volume of BTEQ scripts and stored procedures that need conversion. 2) The use of Teradata-specific functions and query constructs (like QUALIFY, MACROS, SET tables) that have no direct BigQuery equivalent.

Answer

Number of users and concurrent queries.

Answer

Number of tables and rows in the database.

Answer

Availability of network bandwidth between on-premises and GCP.

Question 15

A retail company needs a scalable NoSQL database for a mobile app with offline synchronization, real-time updates, and flexible security rules. The data model is document-based. Which Google Cloud service should they choose?

Accepted Answer

Firestore. Firestore is a fully managed, serverless NoSQL document database that provides offline support, real-time listeners, and security rules for mobile and web apps.

Answer

Memorystore for Redis

Answer

Cloud SQL

Answer

Cloud Bigtable