DBS-C01 Practice Test 10 — 10 Questions

Question 1

A company uses Amazon DynamoDB with fine-grained access control using IAM policies. A developer reports that an application role can read and write to the 'orders' table but cannot perform a Scan operation on a Global Secondary Index (GSI). The IAM policy attached to the role includes 'dynamodb:Scan' and the resource ARN for the table. What is the likely reason for this failure?

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

Accepted Answer

The IAM policy does not include the GSI's ARN in the resource statement.. DynamoDB IAM policies require the resource ARN to match the specific table or index being accessed. A GSI has its own ARN (table-name/index/index-name), so a policy that only includes the base table ARN will allow Scan on the table but deny Scan on the GSI. The fix is to add the GSI's ARN to the Resource element of the policy.

Answer

The policy has a condition that restricts Scan operations based on the time of day.

Answer

The role does not have permission to read from the base table.

Answer

The IAM policy does not allow the 'dynamodb:Scan' action on the table.

Question 2

A company is designing a database for a social media application that needs to handle friend-of-friend queries and recommendation engine traversals. Which AWS database is best suited?

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 ideal for friend-of-friend queries and recommendation engine traversals that require navigating complex relationships with low latency.

Answer

Amazon DynamoDB

Answer

Amazon DocumentDB (with MongoDB compatibility)

Answer

Amazon ElastiCache for Redis

Question 3

A company is using Amazon ElastiCache for Redis as a caching layer. The application is experiencing higher latency than expected. The team suspects that cache evictions are occurring due to memory pressure. Which ElastiCache metric should be monitored to confirm this?

Accepted Answer

Evictions. The `Evictions` metric in ElastiCache for Redis tracks the number of keys evicted due to memory pressure, which directly indicates cache evictions. Option A is incorrect because `CurrConnections` shows the number of current client connections, not evictions. Option C is incorrect because `ReplicationLag` measures the delay between the primary and replica nodes, not evictions. Option D is incorrect because `CacheHits` shows the number of successful key lookups, not evictions.

Answer

CurrConnections

Answer

ReplicationLag

Answer

CacheHits

Question 4

A company is migrating a 2 TB PostgreSQL database from on-premises to Amazon RDS for PostgreSQL with minimal downtime. The database is continuously updated. Which migration strategy should be used?

Accepted Answer

Use AWS Database Migration Service (DMS) with ongoing replication from an on-premises source.. AWS DMS supports ongoing replication (change data capture, CDC) from an on-premises PostgreSQL source to Amazon RDS for PostgreSQL, enabling minimal downtime migration. The 2 TB size is well within DMS's capabilities, and CDC captures incremental changes after the full load, allowing near-zero downtime cutover.

Answer

Use AWS Schema Conversion Tool (SCT) and AWS Snowball to transfer data.

Answer

Use AWS Database Migration Service with a full load only, then cut over.

Answer

Use pg_dump and pg_restore during a maintenance window.

Question 5

A company wants to migrate a 500 GB SQL Server database to Amazon RDS for SQL Server with the least amount of downtime. The on-premises network has a 1 Gbps connection to AWS. Which approach should be used?

Accepted Answer

Use AWS DMS with ongoing replication from on-premises to RDS. AWS DMS with ongoing replication (change data capture, CDC) allows you to perform a full load of the 500 GB database while continuously replicating ongoing changes from the on-premises SQL Server to Amazon RDS for SQL Server. This minimizes downtime to a brief cutover window when you stop writes on the source and redirect traffic to the target. The 1 Gbps connection is sufficient for the initial load and ongoing replication, making this the most effective approach for minimal downtime.

Answer

Use AWS Snowball to transfer the database backup, then restore to RDS

Answer

Copy database files to S3 and then use RDS import

Answer

Use native SQL Server backup to S3, then restore to RDS

Question 6

Match each AWS service to its primary purpose.

Accepted Answer

RDS: Managed relational database service supporting multiple engines. These are core AWS database services with distinct use cases. Common confusions include mixing up Redshift (data warehouse) with ElastiCache (in-memory cache) and Neptune (graph) with DocumentDB (document).

Answer

Redshift: Fully managed in-memory caching service

Answer

ElastiCache: Fully managed petabyte-scale data warehouse

Answer

Neptune: Fully managed document database

Question 7

A company is migrating a 5 TB MySQL database to Amazon Aurora MySQL. The migration must have zero downtime and the source database is continuously written to. The team plans to use AWS DMS with ongoing replication. However, they notice that the target Aurora instance is not receiving all changes from the source. Which configuration change is most likely required to resolve this?

Accepted Answer

Enable binary logging (binlog) on the source MySQL database with row-based logging.. AWS DMS requires binary logging (binlog) with row-based logging on the source MySQL database to capture ongoing changes for continuous replication. Without binlog enabled, DMS cannot read the change data stream needed to replicate transactions to the target Aurora instance, causing missed changes. This is a mandatory prerequisite for any MySQL-to-Aurora migration using DMS with ongoing replication.

Answer

Create an Amazon RDS read replica of the source database and use it as the source endpoint.

Answer

Set the target table preparation mode to 'Do nothing' in the DMS task.

Answer

Configure a VPC endpoint for the DMS replication instance.

Question 8

A company runs a reporting application that queries an Amazon RDS for PostgreSQL database. The queries are complex and take a long time to run, causing performance degradation on the primary instance. The team wants to improve query performance without affecting the transactional workload. Which solution should they use?

Accepted Answer

Create one or more read replicas and direct reporting queries to them. Amazon RDS read replicas allow you to offload read-heavy reporting queries from the primary PostgreSQL instance. By directing complex, long-running queries to one or more read replicas, you eliminate resource contention on the primary instance, preserving transactional workload performance. RDS for PostgreSQL supports up to 15 read replicas, which can be promoted to a primary instance if needed, and they use asynchronous replication to stay nearly current.

Answer

Increase the instance size of the primary database

Answer

Migrate to Amazon RDS for MySQL and use Multi-AZ

Answer

Use Amazon ElastiCache to cache the results of complex queries

Question 9

A database engineer is troubleshooting an Amazon Aurora MySQL DB cluster that is experiencing frequent failovers. The failovers are occurring during periods of low write activity. The engineer notices that the primary instance's writer endpoint is being used for read traffic from a legacy application. What is the most likely cause of the failovers?

Accepted Answer

The primary instance is overloaded due to read traffic from the writer endpoint. Aurora MySQL failovers during low write activity are most likely caused by the primary instance being overloaded with read traffic directed at the writer endpoint. The writer endpoint always points to the primary, so legacy read queries consume CPU, memory, and connection slots on the primary, triggering health checks to fail and forcing a failover. Offloading reads to the reader endpoint would resolve the overload.

Answer

A high replication lag between the primary and replica instances

Answer

A long-running write transaction is blocking the failover

Answer

Insufficient storage for the Aurora cluster volume

Question 10

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. Which TWO methods can the database specialist use to minimize downtime during the migration?

Accepted Answer

Use Oracle GoldenGate to replicate data continuously.. Option B is correct because Oracle GoldenGate performs continuous, near-real-time change data capture and replication from the on-premises Oracle database to RDS for Oracle, so the cutover window is limited to a brief final sync rather than the entire data volume. Option C is correct because AWS DMS supports ongoing (change data capture) replication for Oracle sources, keeping the target RDS for Oracle in sync and allowing a short switchover with minimal downtime. Options A, D, and E are not suitable for minimizing downtime: RMAN backup/restore, full backup/restore, and Data Pump export/import are all one-time bulk operations that require the source to be quiesced and the full dataset to be transferred before cutover, resulting in significant downtime proportional to database size.

Answer

Use Oracle Recovery Manager (RMAN) to back up and restore.

Answer

Take a full database backup and restore to RDS.

Answer

Use Oracle Data Pump to export and import the database.