DBS-C01 Practice Test 2 — 30 Questions

Question 1

A developer accidentally deleted a critical table from an Amazon RDS for MySQL DB instance. Automated backups are enabled with a retention period of 7 days. The deletion occurred 3 hours ago. What is the fastest way to restore the deleted table without affecting other tables?

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

Accepted Answer

Perform a point-in-time restore of the DB instance to a time just before the deletion, then export the table.. Point-in-time recovery (PITR) allows you to restore the entire DB instance to any second within the automated backup retention period (7 days). By restoring to a time just before the deletion, you can then extract the deleted table using mysqldump or SELECT INTO OUTFILE, and import it back into the original instance. This is the fastest method because it leverages existing automated backups without requiring a manual snapshot or waiting for a full restore of a large instance.

Answer

Use the RDS Query Editor to run a flashback query that retrieves the deleted data.

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Restore the DB instance from the latest manual snapshot and extract the table.

Answer

Restore the table from the automated backup using the AWS Management Console table-level restore feature.

Question 2

A company is running a production Amazon DynamoDB table and notices that read requests are being throttled. The table has on-demand capacity mode enabled. Which action should the database specialist take to troubleshoot the throttling?

Accepted Answer

Check the CloudWatch metric 'ThrottledRequests' for the table and review 'SystemErrors' to identify hot partitions.. With on-demand capacity, throttling often results from hot partitions. The CloudWatch metric 'ThrottledRequests' helps detect throttling, and reviewing 'SystemErrors' can indicate partition-level errors, aiding in identifying hot partitions. Option B is incorrect because auto scaling is only supported for provisioned capacity mode, not on-demand. Option C is incorrect because enabling DAX can reduce read load but does not address the root cause of throttling due to hot partitions; it is not a troubleshooting step. Option D is incorrect because switching to provisioned capacity and increasing RCUs is a remediation action, not a troubleshooting action.

Answer

Enable auto scaling on the table to automatically adjust capacity.

Answer

Enable DynamoDB Accelerator (DAX) to reduce read load on the table.

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Switch the table to provisioned capacity mode and increase the read capacity units.

Question 3

The application uses the IAM role to access the 'orders' DynamoDB table. What is the intended effect of this policy?

Accepted Answer

The role can only access items where the partition key matches the principal's identifier. The policy uses a condition key like `dynamodb:LeadingKeys` with a value referencing the principal's identifier (e.g., `${aws:userid}`). This restricts access to only those items in the 'orders' table whose partition key matches the IAM role's unique identifier, enforcing row-level security. The intended effect is fine-grained access control, not full table access or time-based restrictions.

Answer

The role can perform any DynamoDB action on the 'orders' table

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The role can access all items in the table but only during specific times

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The role is denied access to the 'orders' table

Question 4

A database team is migrating an on-premises Oracle database to Amazon Aurora PostgreSQL. The team needs to ensure minimal downtime and data consistency. Which approach should be used?

Accepted Answer

Use AWS Database Migration Service (DMS) with ongoing replication using change data capture (CDC). AWS DMS with ongoing replication using change data capture (CDC) is the correct approach because it enables a live migration with minimal downtime. DMS can perform a full load of the Oracle database and then continuously replicate ongoing changes from Oracle to Aurora PostgreSQL, ensuring data consistency at the point of cutover. This method avoids the need for a long maintenance window and supports heterogeneous migrations with automatic schema conversion.

Answer

Use the PostgreSQL foreign data wrapper (FDW) to link the Oracle database

Answer

Use AWS Server Migration Service (SMS) to replicate the database

Answer

Use pg_dump and pg_restore to migrate the data during a maintenance window

Question 5

A company is using Amazon ElastiCache for Redis to cache database query results. The application team reports that cache hit ratio has dropped significantly. What is the first step to investigate?

Accepted Answer

Check the CacheHitRate and Evictions metrics in CloudWatch. When the cache hit ratio drops significantly, the first step is to investigate whether the cache is evicting keys due to memory pressure or if the working set no longer fits. CloudWatch metrics such as `CacheHitRate` and `Evictions` provide immediate visibility into these conditions without requiring direct Redis access. This aligns with the AWS Well-Architected Framework's principle of observability before making configuration changes.

Answer

Run the Redis INFO command to see memory usage

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Review the ElastiCache event logs for node failures

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Check the Redis AOF persistence logs

Question 6

A company is migrating a PostgreSQL database to Amazon RDS for PostgreSQL. They want to automate the deployment of the RDS instance using infrastructure as code. Which AWS service should they use?

Accepted Answer

AWS CloudFormation.. AWS CloudFormation is the correct service for automating the deployment of an RDS for PostgreSQL instance using infrastructure as code. It allows you to define the entire RDS instance configuration—including DB instance class, storage, backup retention, and security groups—in a declarative JSON or YAML template, which can be version-controlled and reused for consistent, repeatable deployments.

Answer

Amazon EC2 Auto Scaling.

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AWS Management Console.

Answer

AWS Command Line Interface (CLI).

Question 7

A company is migrating a 2 TB Oracle database to Amazon Aurora PostgreSQL. The migration must have minimal downtime and support ongoing replication. Which AWS service should be used?

Accepted Answer

AWS Database Migration Service (AWS DMS). AWS Database Migration Service (AWS DMS) is the correct choice because it supports ongoing replication (change data capture, CDC) from an Oracle source to an Amazon Aurora PostgreSQL target, enabling a migration with minimal downtime. DMS can handle a 2 TB database by using a large replication instance and tuning task settings, and it continuously replicates changes until the cutover is complete.

Answer

AWS DataSync

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Amazon S3 Glacier

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AWS Schema Conversion Tool (AWS SCT)

Question 8

A company is migrating an on-premises PostgreSQL database to Amazon RDS for PostgreSQL. They need to minimize downtime and ensure data consistency. Which TWO methods can be used together to achieve this?

Accepted Answer

Use AWS DMS with full load and CDC. AWS DMS with full load and Change Data Capture (CDC) enables a zero-downtime migration by first copying the existing data (full load) and then continuously replicating ongoing changes from the on-premises PostgreSQL source to the Amazon RDS for PostgreSQL target. This ensures data consistency because CDC captures transactions in near real-time using the PostgreSQL logical replication slot mechanism, allowing the target to stay synchronized until the cutover.

Answer

Take a file system snapshot and copy to Amazon EBS

Answer

Use pg_dump and pg_restore

Answer

Export data to Amazon S3 and import using COPY

Question 9

A company is migrating a 2 TB Oracle database from on-premises to Amazon RDS for Oracle. The database has a 4-hour maintenance window and the migration must have minimal downtime. Which AWS service should be used for the migration?

Accepted Answer

Use AWS Database Migration Service (DMS) with ongoing replication from the source database.. AWS DMS with ongoing replication (change data capture) is the correct choice because it allows you to perform a full load of the 2 TB Oracle database and then continuously replicate incremental changes from the source to the target RDS instance. This minimizes downtime by enabling a cutover window of minutes rather than hours, which is critical given the 4-hour maintenance window constraint.

Answer

Use AWS Schema Conversion Tool (SCT) to convert the schema and then perform a full data load.

Answer

Create an RDS Cross-Region Read Replica and promote it to a standalone instance.

Answer

Take a full backup of the on-premises database, upload it to S3, and restore it to RDS.

Question 10

Which THREE factors should be considered when choosing between a homogeneous migration and a heterogeneous migration to Amazon RDS? (Select THREE.)

Accepted Answer

Performance requirements of the target database.. A homogeneous migration (e.g., MySQL to RDS MySQL) typically requires minimal schema changes, preserves performance characteristics, and maintains existing licensing costs. A heterogeneous migration (e.g., Oracle to RDS PostgreSQL) requires schema conversion (validating schema compatibility), may require re-architecting to meet performance requirements due to different query optimizers, and can change licensing costs (e.g., eliminating Oracle licenses). Therefore, factors B, D, and E directly influence the choice between homogeneous and heterogeneous migrations.

Answer

Network latency between source and target.

Answer

Amount of application code changes needed.

Question 11

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 12

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

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Amazon DynamoDB

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Amazon ElastiCache for Redis

Question 13

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 14

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

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The new primary has a smaller instance size

Answer

Automated backups are running on the new primary

Question 15

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 16

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

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Amazon ElastiCache for Redis

Answer

Amazon RDS for MySQL

Question 17

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 18

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 19

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 20

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