DBS-C01 Practice Questions 2 — 50 Questions

Question 1

A security engineer is designing a VPC with an RDS instance. The database must not be accessible from the internet, but EC2 instances in a private subnet must connect. Which security group configuration is MOST secure?

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

Accepted Answer

Set the RDS security group inbound rule to allow traffic from the EC2 security group on port 3306.. The most secure because it uses a security group reference instead of a CIDR block. By referencing the EC2 security group as the source in the RDS security group inbound rule, only instances associated with that specific security group can communicate with the database on port 3306. This approach adheres to the principle of least privilege and automatically scales as instances are added or removed from the EC2 security group, without needing to update CIDR ranges.

Answer

Set the RDS security group inbound rule to allow traffic from the VPC CIDR on port 3306.

Answer

Set the RDS security group inbound rule to allow traffic from 0.0.0.0/0 on port 3306.

Answer

Set the RDS security group inbound rule to allow traffic from the private subnet CIDR on port 3306.

Question 2

A company needs to migrate a SQL Server database to Amazon RDS for SQL Server. The database uses stored procedures with xp_cmdshell. What should the company do?

Accepted Answer

Rewrite the stored procedures to remove dependency on xp_cmdshell before migration.. Amazon RDS for SQL Server does not support the xp_cmdshell extended stored procedure because it allows execution of operating system commands, which violates the managed service model where AWS controls the host OS. The correct approach is to rewrite the stored procedures to remove dependency on xp_cmdshell before migration, using alternatives such as SQL Server Agent jobs, CLR integration, or external scripting via AWS Lambda or EC2.

Answer

Use RDS Custom for SQL Server to retain full control.

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Enable xp_cmdshell in the RDS parameter group.

Answer

Disable xp_cmdshell in the stored procedures and migrate as-is.

Question 3

A company is migrating an on-premises MongoDB database to AWS. Which AWS database service is most compatible and requires minimal application changes?

Accepted Answer

Amazon DocumentDB (with MongoDB compatibility).. Amazon DocumentDB (with MongoDB compatibility) is the most compatible AWS database service for migrating an on-premises MongoDB database because it is purpose-built to emulate the MongoDB wire protocol and data model, allowing existing MongoDB drivers and tools to connect with minimal or no application code changes. This makes it the ideal choice for a lift-and-shift migration that preserves the document-oriented structure and query patterns of MongoDB.

Answer

Amazon DynamoDB.

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Amazon Neptune.

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Amazon RDS for MySQL.

Question 4

A company is experiencing slow query performance on an Amazon RDS for MySQL database. The DBA wants to identify the most time-consuming queries. Which TWO actions should the DBA take? (Choose two.)

Accepted Answer

Use Amazon RDS Performance Insights.. Amazon RDS Performance Insights (Option D) provides a database performance tuning and monitoring feature that visualizes database load and identifies the most time-consuming queries by breaking down wait events, SQL statements, and hosts. It directly helps the DBA pinpoint the specific queries causing performance degradation without additional configuration or overhead.

Answer

Enable the audit log.

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Enable the general log and review it.

Answer

Use Amazon RDS Enhanced Monitoring.

Question 5

A company is migrating a 5 TB Oracle database to Amazon RDS for Oracle. The database has several large tables with LOB columns. The migration must have minimal downtime. Which approach should be taken?

Accepted Answer

Use AWS DMS with LOB support and ongoing replication from Oracle to RDS.. AWS DMS with LOB support and ongoing replication (change data capture, CDC) is the correct approach because it enables a near-zero downtime migration by continuously replicating changes from the source Oracle database to Amazon RDS for Oracle after an initial full load. DMS handles large LOB columns efficiently using its 'Full LOB mode' or 'Limited LOB mode' settings, which are critical for tables with LOB data. The combination of full load + CDC ensures minimal downtime, as the target remains synchronized until cutover.

Answer

Use Oracle GoldenGate to replicate data to RDS.

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Use Oracle Data Pump to export the database and import into RDS.

Answer

Copy the database files to Amazon S3 and use the rdsadmin.rds_restore_from_s3 procedure.

Question 6

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.. Amazon RDS (relational database service) requires a predefined schema with tables, columns, and data types before data can be inserted, enforcing ACID compliance and referential integrity. In contrast, Amazon DynamoDB is a NoSQL key-value and document database that is schema-less, allowing you to store items with varying attributes without upfront schema definition, which is ideal for agile development and unstructured data.

Answer

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

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Only RDS supports Multi-AZ deployments for high availability.

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Both services support encryption at rest and in transit.

Question 7

A company is migrating an on-premises MySQL database to Amazon RDS for MySQL. The database has a large table with frequent inserts and updates. To minimize downtime during migration, which AWS service should be used?

Accepted Answer

AWS Database Migration Service (DMS). AWS Database Migration Service (DMS) is the correct choice because it supports ongoing replication (change data capture, CDC) from an on-premises MySQL source to Amazon RDS for MySQL, allowing the source database to remain fully operational during the migration. This minimizes downtime by continuously applying inserts and updates from the source to the target until you perform the final cutover, which can be a brief pause of seconds to minutes.

Answer

Amazon RDS read replica

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AWS Schema Conversion Tool (SCT)

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AWS Glue

Question 8

A company runs a MySQL-compatible database on Amazon RDS for a mission-critical application. The database experiences high write latency due to frequent index updates. The team wants to redesign the database to reduce write amplification and improve insert performance. Which TWO design changes could help?

Accepted Answer

Use batch INSERT statements instead of single-row inserts. Batch INSERT statements reduce the overhead of per-row index updates by combining multiple rows into a single transaction. This minimizes the number of index tree traversals and log flushes, directly lowering write amplification and improving insert throughput in InnoDB.

Answer

Switch the storage engine from InnoDB to MyISAM

Answer

Upgrade to a larger RDS instance class

Answer

Normalize the database schema to reduce data redundancy

Question 9

A company is planning to migrate a 1 TB MySQL database from on-premises to Amazon RDS for MySQL. The migration must have minimal downtime and support ongoing replication. Which THREE steps should the company include in the migration plan? (Choose THREE.)

Accepted Answer

Set up an AWS Direct Connect or VPN connection between on-premises and AWS.. A stable, low-latency network connection (Direct Connect or VPN) is essential for AWS DMS to perform ongoing replication with minimal downtime. Without this, the replication can be interrupted by network issues, causing data loss or extended cutover windows.

Answer

Deploy an Amazon EC2 instance to act as a proxy for the DMS replication.

Answer

Install the AWS Schema Conversion Tool on the source server to convert the schema.

Question 10

A developer is trying to create a FULLTEXT index on a column in an RDS MySQL instance. The error log shows the index creation failed. What is the most likely cause?

Accepted Answer

The column 'description' has a length that exceeds the maximum allowed for FULLTEXT index.. In RDS MySQL, FULLTEXT indexes have a maximum column length limit of 1000 bytes for InnoDB and 1000 characters for MyISAM. If the 'description' column exceeds this limit, the index creation will fail. This is the most likely cause because the error log indicates a failure without other configuration issues.

Answer

The table size is too large for a FULLTEXT index to be created.

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The table uses a character set that is not compatible with FULLTEXT indexes.

Answer

The InnoDB engine does not support FULLTEXT indexes.

Question 11

A company is deploying a globally distributed application with users in the US, Europe, and Asia. The application requires sub-10ms read latency for user profiles stored in Amazon DynamoDB. Writes are less frequent. Which configuration meets the latency requirement while minimizing write conflicts?

Accepted Answer

Use DynamoDB global tables to replicate data to Regions close to users.. DynamoDB global tables provide multi-region, multi-active replication with eventual consistency, enabling sub-10ms reads from local replicas while writes are replicated asynchronously. This minimizes write conflicts because DynamoDB uses last-writer-wins (LWW) conflict resolution, which is acceptable for user profiles where writes are infrequent and conflicts are rare.

Answer

Deploy Amazon RDS for MySQL with Multi-AZ and cross-Region read replicas.

Answer

Use Amazon ElastiCache for Redis Global Datastore with DynamoDB as backing store.

Answer

Deploy a single DynamoDB table in us-east-1 with DAX caches in each region.

Question 12

A company is designing a database for an IoT application that ingests millions of sensor readings per second. Each reading includes device ID, timestamp, and measurement. The workload requires time-series analytics and data retention for 90 days. Which AWS database solution is MOST appropriate?

Accepted Answer

Amazon Timestream. Amazon Timestream is a purpose-built time-series database designed for IoT and operational applications that ingest millions of sensor readings per second. It automatically manages data retention policies (e.g., 90 days) by storing recent data in memory and historical data in a cost-optimized store, and it supports time-series analytics with built-in functions like interpolation and smoothing.

Answer

Amazon Redshift with auto-copy from S3

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Amazon ElastiCache for Redis with time-series module

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Amazon DynamoDB with TTL

Question 13

A financial services company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database has a high volume of write transactions and requires minimal downtime during migration. Which AWS service or feature should be used to replicate data continuously to the target RDS instance during the migration?

Accepted Answer

AWS Database Migration Service (AWS DMS) with ongoing replication. AWS Database Migration Service (AWS DMS) with ongoing replication (change data capture, CDC) is the correct choice because it continuously captures and applies changes from the source Oracle database to the target Amazon RDS for Oracle instance, enabling near-zero downtime during migration. This is achieved by using Oracle's redo logs to stream transactions in real time, which meets the high write volume and minimal downtime requirements.

Answer

Amazon RDS Read Replica

Answer

Amazon RDS Multi-AZ deployment

Answer

AWS Schema Conversion Tool (AWS SCT)

Question 14

A company is migrating a large Oracle data warehouse to AWS. The warehouse contains 50 TB of data and runs complex analytical queries. The solution must support concurrency of up to 100 users and provide high performance for queries. Which THREE design decisions should the company make? (Choose three.)

Accepted Answer

Use distribution keys based on frequently joined columns. Distribution keys based on frequently joined columns ensure that related data is co-located on the same compute nodes, minimizing data movement across the network during joins. This is critical for complex analytical queries on large datasets in Amazon Redshift, as it reduces shuffle overhead and improves query performance.

Answer

Use Amazon RDS for Oracle with Multi-AZ

Answer

Use Amazon DynamoDB with global tables

Question 15

A company is designing a database for an e-commerce platform that requires high availability and automatic failover with minimal downtime. The application performs both OLTP and read-heavy analytics. Which AWS database service should be used?

Accepted Answer

Amazon Aurora. Amazon Aurora is the correct choice because it combines the high availability and automatic failover of a relational database with the performance needed for both OLTP and read-heavy analytics. Aurora provides six-way replication across three Availability Zones, automatic failover in under 30 seconds, and supports up to 15 low-latency read replicas that can offload analytics queries without impacting write performance.

Answer

Amazon DynamoDB

Answer

Amazon RDS for MySQL

Answer

Amazon Redshift

Question 16

A company is migrating a 10 TB Oracle data warehouse to Amazon Redshift. The migration must minimize data transfer costs and ensure data integrity. Which TWO steps should the company take?

Accepted Answer

Use AWS Schema Conversion Tool (SCT) to convert the Oracle schema to Redshift. The AWS Schema Conversion Tool (SCT) is specifically designed to convert Oracle database schemas to Amazon Redshift-compatible schemas, handling data type mappings, stored procedures, and other schema objects. This step is critical for a successful migration as it ensures the target schema is optimized for Redshift's columnar storage and MPP architecture, reducing manual rework and potential data integrity issues.

Answer

Use AWS DMS to replicate data directly over the internet

Answer

Use Amazon Kinesis Data Streams to stream data to Redshift

Answer

Use Amazon Redshift Spectrum to query data in S3 after loading

Question 17

A company is designing a database for a social media application that requires low-latency access to user profiles and support for complex graph queries. Which AWS database service is most suitable for this workload?

Accepted Answer

Amazon Neptune. Amazon Neptune is a fully managed graph database service optimized for storing and querying highly connected data. It supports both property graph (Apache TinkerPop/Gremlin) and RDF (SPARQL) models, making it the ideal choice for social media applications that require low-latency traversal of complex relationships, such as friend-of-friend recommendations or influence paths.

Answer

Amazon DynamoDB

Answer

Amazon ElastiCache for Redis

Answer

Amazon RDS for MySQL

Question 18

Match each AWS monitoring tool to its capability for databases.

Accepted Answer

Amazon CloudWatch: Monitors AWS resources and applications, provides metrics and logs. Correct matches: CloudWatch monitors metrics and logs, Performance Insights analyzes database load, Enhanced Monitoring provides OS-level metrics, and CloudTrail records API activity. Common confusions include mixing Enhanced Monitoring with CloudWatch and Performance Insights with CloudTrail.

Answer

Amazon CloudWatch: Provides OS-level metrics for RDS instances

Answer

Amazon RDS Performance Insights: Records API calls for database actions

Question 19

A company is using Amazon RDS for PostgreSQL for its transactional database. The application generates reports that query millions of rows, causing high CPU on the primary instance. The reports are not time-sensitive. What is the MOST cost-effective way to offload the reporting queries without affecting write performance?

Accepted Answer

Create an Amazon RDS Read Replica and direct reporting queries to the replica.. Creating an Amazon RDS Read Replica offloads reporting queries to a separate read-only instance, preventing CPU contention on the primary. Since the reports are not time-sensitive, the replica can handle the large queries without impacting write performance, and it is cost-effective because you only pay for the replica's compute and storage.

Answer

Use Amazon ElastiCache to cache report results.

Answer

Enable Multi-AZ to distribute reads to the standby instance.

Answer

Migrate reporting to Amazon Redshift.

Question 20

A developer sees the above key schema for the ProductCatalog table. Which query will be most efficient for retrieving a single item?

Accepted Answer

GetItem with ProductId = '123' and Category = 'Books'. The ProductCatalog table's primary key is a composite key of Category (partition key) and ProductId (sort key). A GetItem operation with both the partition key and sort key provides the most efficient direct access to a single item, as it uses the primary key to retrieve the item with exactly one read operation, without any filtering or scanning.

Answer

Query with Category = 'Books'

Answer

GetItem with ProductId = '123'

Answer

Scan the table and filter by ProductId