DBS-C01 Practice Test 18 — 15 Questions

Question 1

A company is designing a database for a global IoT application that ingests millions of events per second. Each event includes a device ID, timestamp, and sensor readings. The requirement is to store data for historical analysis and to support queries that aggregate data by device ID over time ranges. The team needs a cost-effective solution that can scale write throughput. Which database design is most appropriate?

Accepted Answer

Use Amazon DynamoDB with a table keyed by device ID (partition) and timestamp (sort).. Option D is correct because DynamoDB with a partition key of device ID and sort key of timestamp allows high write throughput and efficient time-range queries. Option A is wrong because RDS with auto-scaling cannot handle millions of events per second. Option B is wrong because Redshift is optimized for analytics but not for high-velocity writes. Option C is wrong because ElastiCache is in-memory and too expensive for historical storage.

Answer

Use Amazon RDS for MySQL with Multi-AZ and auto-scaling storage.

Answer

Use Amazon Redshift with a schema optimized for time-series data.

Answer

Use Amazon ElastiCache for Redis with persistence enabled.

Question 2

A company runs an e-commerce platform on Amazon Aurora MySQL. The platform experiences high traffic during flash sales. To handle the load, they want to offload read traffic to read replicas. However, they are concerned about replication lag causing stale data for inventory checks. Which three strategies can reduce replication lag? (Choose three.)

Accepted Answer

Enable binary log replication with parallel apply on replicas.. Option A (Use Aurora Auto Scaling) is correct because it adds replicas to distribute load. Option B (Use Binary Log Replication with parallel apply) is correct because it improves replication throughput. Option D (Use lower isolation levels on replicas) is correct because it reduces locking and improves apply speed. Option C is wrong because increasing instance size of replicas helps, but not of the writer; the bottleneck is replica apply. Option E is wrong because synchronous replication would impact write performance.

Answer

Implement synchronous replication between writer and replicas.

Answer

Increase the instance size of the writer instance.

Question 3

A company is designing a document management system using Amazon DocumentDB. Each document is up to 10 MB. The application needs to retrieve multiple documents by their IDs in a single request. The IDs are known at query time. Which query pattern is most efficient?

Accepted Answer

Use a find operation with the $in operator on the _id field.. Option B is correct because $in operator allows a single query to fetch multiple documents by ID. Option A is wrong because scanning is inefficient. Option C is wrong because parallel queries increase overhead. Option D is wrong because $or is less efficient than $in for the same field.

Answer

Use a find operation with the $or operator on the _id field.

Answer

Use a scan operation with a filter on the _id field.

Answer

Issue multiple get operations in parallel.

Question 4

Which TWO factors should you consider when choosing between Amazon RDS and Amazon DynamoDB for a new application?

Accepted Answer

RDS requires a predefined schema, while DynamoDB is schema-less.. Option B is correct because DynamoDB uses a NoSQL model, while RDS uses relational. Option E is correct because DynamoDB supports flexible schema, while RDS requires fixed schema. Option A is wrong because both support encryption. Option C is wrong because both support VPC. Option D is wrong because both support multi-AZ deployments (RDS Multi-AZ, DynamoDB global tables).

Answer

DynamoDB can only be accessed from within a VPC, while RDS can be public.

Answer

Only RDS supports Multi-AZ deployments for high availability.

Answer

Both services support encryption at rest and in transit.

Question 5

A company wants to run a graph database for a social network application. The data model involves users, posts, comments, and likes, with many-to-many relationships. Which AWS database service is most appropriate?

Accepted Answer

Amazon Neptune. Amazon Neptune is a fully managed graph database service optimized for highly connected data. DynamoDB is NoSQL but not graph. RDS is relational, which can model graphs but with complex queries. DocumentDB is document-based.

Answer

Amazon RDS for PostgreSQL

Answer

Amazon DocumentDB

Answer

Amazon DynamoDB

Question 6

A company uses Amazon Aurora MySQL for a SaaS application. Each tenant has a separate database. The company wants to implement a centralized monitoring solution that collects performance metrics from all tenant databases. The solution should be cost-effective and require minimal overhead. Which approach should be used?

Accepted Answer

Use Amazon CloudWatch Agent to collect custom metrics from each Aurora instance and aggregate in CloudWatch.. Option C is correct because Amazon CloudWatch Agent installed on each Aurora instance can collect custom metrics, but more efficiently, Aurora publishes Performance Insights metrics to CloudWatch. Option A is wrong because a single RDS instance cannot host multiple databases for isolation. Option B is wrong because DMS is for data migration, not monitoring. Option D is wrong because a Lambda function querying each database would create overhead.

Answer

Use AWS DMS to continuously replicate metrics to a central RDS instance.

Answer

Consolidate all tenants into a single RDS MySQL instance and use separate schemas.

Answer

Run an AWS Lambda function that queries each database's performance_schema every minute and stores results in S3.

Question 7

A startup is building a multi-tenant SaaS application where each tenant's data must be isolated. The data model is relational with complex joins. Which database deployment model is most appropriate?

Accepted Answer

Provision a separate Amazon RDS instance for each tenant. Option B is correct because a separate RDS instance per tenant provides strong isolation. Option A (single table with tenant_id) risks noisy neighbors. Option C (DynamoDB single table) is not relational. Option D (Redshift) is for analytics, not OLTP.

Answer

Use a single Amazon DynamoDB table with a tenant_id partition key

Answer

Use a single Amazon Redshift cluster with tenant_id distribution key

Answer

Use a single Amazon RDS database with a tenant_id column on every table

Question 8

A company is designing a relational database for an e-commerce application that requires high availability and automated failover across AWS Regions. Which AWS database service should they use?

Accepted Answer

Amazon Aurora Global Database. Amazon Aurora Global Database provides cross-Region replication and automated failover, meeting the high availability requirements. Option A (DynamoDB) is NoSQL, not relational. Option B (RDS Multi-AZ) is single-Region. Option D (Redshift) is a data warehouse, not for OLTP.

Answer

Amazon DynamoDB Global Tables

Answer

Amazon RDS with Multi-AZ deployment

Answer

Amazon Redshift with cross-Region snapshot copy

Question 9

Which THREE factors should be considered when choosing between Amazon DynamoDB and Amazon Aurora for a new application? (Select THREE.)

Accepted Answer

Access patterns (key-value vs relational queries). Access pattern (key-value vs relational), transaction support (Aurora supports complex transactions), and scalability model (DynamoDB scales horizontally) are key. Data size and cost are not primary differentiators.

Answer

Cost per GB of storage

Answer

Maximum data size per table

Question 10

A company wants to migrate an on-premises Oracle database to Amazon RDS for Oracle with minimal downtime. Which AWS service should be used for the migration?

Accepted Answer

AWS Database Migration Service (DMS). AWS Database Migration Service (DMS) is designed for migrating databases to AWS with minimal downtime. AWS Schema Conversion Tool (SCT) is used for schema conversion but not for the actual data migration. Service Control Policies (SCP) and Systems Manager are not relevant for database migration.

Answer

AWS Systems Manager

Answer

AWS Schema Conversion Tool (SCT)

Answer

AWS Service Control Policies (SCP)

Question 11

A company needs to store time-series data from IoT sensors. Each sensor sends a reading every minute. The data is rarely accessed after 30 days. The query pattern is to retrieve all readings for a specific sensor within a time range. Which AWS database is most cost-effective?

Accepted Answer

Amazon Timestream. Option B is correct because Timestream is purpose-built for time-series data with automatic tiering. Option A is wrong because DynamoDB is more expensive for this pattern. Option C is wrong because RDS is not optimized for time-series. Option D is wrong because Redshift is for analytics, not real-time ingestion.

Answer

Amazon Redshift

Answer

Amazon DynamoDB with Time-to-Live (TTL)

Answer

Amazon RDS for PostgreSQL with partitioning

Question 12

A company runs a financial application that requires ACID transactions on a relational database. The workload has a high volume of writes and reads, and the team wants to minimize operational overhead. Which AWS database service should they choose?

Accepted Answer

Amazon Aurora (MySQL-compatible). Option C is correct because Amazon Aurora provides MySQL/PostgreSQL compatibility with ACID transactions and higher throughput than standard RDS, reducing overhead. Option A is wrong because DynamoDB is NoSQL and does not support ACID across multiple items by default. Option B is wrong because ElastiCache is in-memory and not ACID-compliant. Option D is wrong because RDS for Oracle requires licensing and more operational overhead compared to Aurora.

Answer

Amazon RDS for Oracle

Answer

Amazon DynamoDB with transactions enabled

Answer

Amazon ElastiCache for Memcached

Question 13

A startup is building a social media application. User profiles, posts, and comments have relationships but the team expects rapid growth and wants to scale horizontally with no single points of failure. They need a database that supports flexible schemas for different content types. Which database service is most appropriate?

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is a fully managed NoSQL key-value and document database that scales horizontally, is highly available, and supports flexible schemas. RDS is relational with fixed schemas. Redshift is for analytics. Neptune is for graph databases, not general purpose.

Answer

Amazon Neptune

Answer

Amazon Redshift

Answer

Amazon RDS for MySQL

Question 14

A company is designing a database for a global application that requires active-active replication across two AWS Regions. The database must support multi-master writes with conflict resolution. Which AWS database service should they use?

Accepted Answer

Amazon DynamoDB Global Tables. Amazon DynamoDB Global Tables provide multi-Region, multi-master replication with conflict resolution based on last writer wins. Aurora Global Database supports replication but is primary-secondary (single master for writes). RDS Multi-AZ is multi-AZ, not multi-Region. Redshift is not designed for this.

Answer

Amazon Aurora Global Database

Answer

Amazon Redshift

Answer

Amazon RDS for MySQL with Multi-AZ

Question 15

A company needs to migrate an on-premises PostgreSQL database to Amazon Aurora PostgreSQL. The database is 2 TB in size and has a 24/7 uptime requirement. Which AWS service should be used to perform the migration with minimal downtime?

Accepted Answer

AWS Database Migration Service (DMS). Option B is correct because AWS Database Migration Service (DMS) supports minimal-downtime migrations using change data capture (CDC). Option A is wrong because S3 is for storage, not database migration. Option C is wrong because the AWS Schema Conversion Tool (SCT) converts schemas but does not perform data migration. Option D is wrong because pg_dump requires downtime for consistent export.

Answer

AWS Schema Conversion Tool (SCT)

Answer

AWS S3

Answer

pg_dump and pg_restore