DBS-C01 Practice Exam 3 — 20 Questions

Question 1

A company is deploying a multi-AZ Aurora MySQL database. They need to ensure that failover happens automatically with minimal data loss. Which configuration should be used?

Accepted Answer

Create an Aurora cluster with one primary and two readers in different Availability Zones.. An Aurora cluster with one primary and two readers in different Availability Zones provides automatic failover with minimal data loss. Aurora uses a shared cluster volume that is replicated six ways across three AZs, ensuring that during a failover, the promoted reader has access to all committed transactions with no data loss. This configuration meets the requirement for multi-AZ high availability and automatic failover within a single region.

Answer

Deploy an Aurora Global Database with a primary in one region and a secondary in another region.

Answer

Use a Multi-AZ RDS for MySQL deployment.

Answer

Configure a single-AZ Aurora instance and enable cross-Region replication.

Question 2

A company is migrating an on-premises Oracle data warehouse to AWS. The warehouse contains 20 TB of data and supports complex SQL queries with joins and aggregations. The migration should minimize downtime and require minimal changes to existing SQL queries. Which database service is MOST appropriate?

Accepted Answer

Amazon Redshift. Amazon Redshift is the most appropriate choice because it is a fully managed, petabyte-scale data warehouse service designed for complex SQL queries with joins and aggregations. It supports standard SQL with minimal changes to existing queries, and its columnar storage and massively parallel processing (MPP) architecture are optimized for analytical workloads. The 20 TB data size and requirement to minimize downtime align with Redshift's ability to perform online resizing and use features like RA3 nodes with managed storage for elastic scaling.

Answer

Amazon RDS for Oracle

Answer

Amazon DynamoDB

Answer

Amazon ElastiCache for Redis

Question 3

Which TWO of the following are recommended best practices for designing a relational database on Amazon RDS? (Select TWO.)

Accepted Answer

Use read replicas to scale read-heavy workloads. Amazon RDS read replicas offload read traffic from the primary DB instance, improving performance for read-heavy workloads by providing additional read-only endpoints. This is a core best practice for scaling read capacity without increasing load on the source instance.

Answer

Use LOB data types to store large text fields

Answer

Use non-EBS-optimized instances to reduce costs

Answer

Store large binary objects (BLOBs) in the database

Question 4

A company uses Amazon RDS for PostgreSQL with Multi-AZ. The primary instance fails and a failover occurs. After failover, the application reports elevated write latency. Which TWO are possible causes?

Accepted Answer

The buffer pool is not warm on the new primary. After a Multi-AZ failover, the new primary instance starts with a cold buffer pool (no cached data blocks). PostgreSQL relies on shared buffers to cache frequently accessed data; without a warm cache, every read request must fetch data from disk, which increases I/O and write latency because writes often require reading the affected pages first. This is a known behavior in RDS for PostgreSQL after failover, and it resolves as the buffer pool warms up over time.

Answer

A read replica is now promoting to primary

Answer

The new primary has a smaller instance size

Answer

Automated backups are running on the new primary

Question 5

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database size is 500 GB. The migration must have minimal downtime. Which AWS service should be used to perform the migration?

Accepted Answer

AWS Database Migration Service (DMS). AWS Database Migration Service (DMS) is the correct choice because it supports heterogeneous migrations from Oracle to Amazon RDS for Oracle with minimal downtime. DMS can perform continuous replication using Oracle's change data capture (CDC) via LogMiner or binary reader, allowing the source database to remain operational during the migration. This makes it ideal for a 500 GB database where downtime must be minimized.

Answer

AWS Snowball Edge

Answer

AWS DataSync

Answer

Amazon RDS for Oracle snapshot copy

Question 6

A company is building a document management system where each document can have multiple attributes (tags) that need to be queried efficiently. The workload is write-heavy with occasional reads. Which database is best suited?

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is the best choice for a write-heavy, document management system with tag-based queries because it is a fully managed NoSQL key-value and document database that delivers single-digit millisecond performance at any scale. Its flexible schema allows each document to have multiple attributes (tags) without predefined schemas, and its secondary indexes (LSI/GSI) enable efficient querying on those tags. DynamoDB's auto-scaling and provisioned throughput are designed to handle high write volumes, while occasional reads benefit from its consistent low-latency access.

Answer

Amazon QLDB

Answer

Amazon ElastiCache for Redis

Answer

Amazon RDS for MySQL

Question 7

A company needs to store and query time-series data from IoT devices. The data arrives in high volume and requires efficient range queries over time. Which database is most appropriate?

Accepted Answer

Amazon Timestream. Amazon Timestream is a purpose-built time-series database that automatically scales to handle high-volume IoT data and is optimized for efficient range queries over time. It separates storage into a memory store for recent data and a magnetic store for historical data, enabling fast queries across time ranges with built-in time-series functions.

Answer

Amazon RDS for MySQL

Answer

Amazon DynamoDB

Answer

Amazon Redshift

Question 8

Which TWO database services are most suitable for workloads that require ACID transactions?

Accepted Answer

Amazon Aurora. Amazon Aurora is correct because it is a MySQL- and PostgreSQL-compatible relational database engine that provides full ACID (Atomicity, Consistency, Isolation, Durability) transaction support, including multi-statement transactions with commit and rollback. Aurora uses a distributed, fault-tolerant storage subsystem that replicates data across three Availability Zones, ensuring durability and consistency for transactional workloads.

Answer

Amazon Neptune

Answer

Amazon Timestream

Answer

Amazon DynamoDB

Question 9

A company is migrating a 100 GB SQL Server database to Amazon RDS for SQL Server. They need to minimize downtime and ensure that only the schema is converted. Which tool should they use?

Accepted Answer

AWS Schema Conversion Tool (SCT). AWS Schema Conversion Tool (SCT) is the correct choice because it is specifically designed to convert database schemas (including stored procedures, functions, and data types) from one engine to another, such as SQL Server to Amazon RDS for SQL Server. Since the requirement is to minimize downtime and only convert the schema (not migrate data), SCT can perform an offline schema conversion without impacting the source database, whereas DMS is a continuous data replication tool that would incur downtime for schema changes.

Answer

AWS Database Migration Service (DMS)

Answer

AWS DMS with schema conversion enabled

Answer

SQL Server Management Studio (SSMS)

Question 10

A company is building a social network application that needs to store user profiles, friend relationships, and a feed of posts. The feed queries are complex, involving graph traversals (e.g., friends of friends). Which database is best suited for the relationship data?

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 and RDF models, and it uses graph traversal languages like Gremlin and SPARQL, making it ideal for complex friend-of-friend queries and social network relationship data.

Answer

Amazon DynamoDB

Answer

Amazon RDS for MySQL

Answer

Amazon ElastiCache for Redis

Question 11

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?

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 12

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.

Answer

Enable xp_cmdshell in the RDS parameter group.

Answer

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

Question 13

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.

Answer

Amazon Neptune.

Answer

Amazon RDS for MySQL.

Question 14

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.

Answer

Enable the general log and review it.

Answer

Use Amazon RDS Enhanced Monitoring.

Question 15

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.

Answer

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 16

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.

Answer

Only RDS supports Multi-AZ deployments for high availability.

Answer

Both services support encryption at rest and in transit.

Question 17

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

Answer

AWS Schema Conversion Tool (SCT)

Answer

AWS Glue

Question 18

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 19

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 20

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.

Answer

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

Answer

The InnoDB engine does not support FULLTEXT indexes.