DBS-C01 Practice Test 48 — 15 Questions

Question 1

A company has a production Amazon DynamoDB table with on-demand capacity. The table experiences occasional throttling due to hot partitions. The operations team wants to implement a solution to identify the specific partition keys causing the throttling. What is the MOST efficient approach?

Accepted Answer

Enable Amazon CloudWatch Contributor Insights for DynamoDB.. Option D is correct because Amazon CloudWatch Contributor Insights can analyze DynamoDB logs and identify the most accessed partition keys, helping to pinpoint hot partitions. Option A is incorrect because CloudWatch Logs Insights requires enabling VPC Flow Logs, which is not specific to DynamoDB. Option B is incorrect because AWS X-Ray traces requests but does not provide partition-level metrics. Option C is incorrect because DynamoDB Streams capture changes, not access patterns.

Answer

Enable AWS X-Ray tracing on the application and analyze traces.

Answer

Enable VPC Flow Logs and use CloudWatch Logs Insights to query the logs.

Answer

Enable DynamoDB Streams and process the stream records to identify hot keys.

Question 2

A company is using a Multi-AZ RDS for MySQL instance. The primary instance recently experienced an unexpected failover, and the application experienced a brief interruption. The database administrator wants to investigate the root cause. Which AWS service should be used to review the failover event and its details?

Accepted Answer

AWS Support (Trusted Advisor). AWS Support provides detailed logs and analysis for events like failovers through the AWS Support API and AWS Support Center. CloudTrail records API calls, RDS events show notifications but not deep root cause analysis, and Config tracks configuration changes. The correct service for RCA is AWS Support.

Answer

AWS Config

Answer

Amazon RDS Event Notifications

Answer

AWS CloudTrail

Question 3

A company is using Amazon DynamoDB with provisioned capacity for a table that experiences unpredictable traffic spikes. The table's read capacity is often underutilized, but occasionally throttling occurs. Which THREE steps should be taken to improve performance and cost? (Choose THREE.)

Accepted Answer

Switch the table to on-demand capacity mode.. Switching to on-demand capacity handles unpredictable spikes automatically and reduces throttling. Using DynamoDB Accelerator (DAX) reduces read load by caching. Auto scaling adjusts capacity based on load, but on-demand is better for unpredictable spikes. Reducing read capacity units would worsen throttling. Disabling auto scaling is counterproductive.

Answer

Reduce the provisioned read capacity units to save cost.

Answer

Disable auto scaling to avoid cost fluctuations.

Question 4

A company has an Amazon DynamoDB table that stores IoT sensor data. The table has a partition key of device_id and a sort key of timestamp. The team wants to efficiently retrieve the latest reading for each device. Which query pattern should be used?

Accepted Answer

Query with ScanIndexForward=false and Limit=1. Option A is correct because using the Query API with ScanIndexForward set to false and Limit 1 will return the most recent item for a given partition key. Option B is wrong because ScanIndexForward=true returns items in ascending order, which would give the oldest item first. Option C is wrong because Scan operations scan the entire table and are inefficient. Option D is wrong because GetItem requires both partition and sort key; the sort key value is not known in advance.

Answer

Scan with FilterExpression to get the latest timestamp for each device

Answer

Query with ScanIndexForward=true and Limit=1

Answer

GetItem with the device_id and timestamp values

Question 5

A company runs an Amazon Redshift cluster with three nodes. The data warehouse team notices that some queries are slow due to high disk usage. The cluster has reached 80% storage capacity. What is the MOST cost-effective way to increase storage without interrupting operations?

Accepted Answer

Perform an elastic resize to change to a node type with larger storage per node.. Option C is correct because Redshift allows resizing to a larger node type, but that can be expensive. Option A is wrong because adding nodes increases both storage and compute, but may be more cost-effective depending on needs. Option C (elastic resize) is the best as it changes node type quickly with minimal downtime. Option D is wrong because adding a node group is not a concept in Redshift.

Answer

Add one more node of the same type to the cluster.

Answer

Use classic resize to change to a node type with larger storage.

Answer

Create a second cluster and use Redshift Spectrum to offload queries.

Question 6

A company attaches the above IAM policy to a user. The user tries to modify the DB instance 'prod-db' in us-east-1. What is the result?

Accepted Answer

The user cannot modify prod-db.. Option C is correct because the Deny statement explicitly denies ModifyDBInstance on prod-db, overriding the Allow. Option A is incorrect because Deny overrides Allow. Option B is incorrect because the Deny is specific to prod-db. Option D is incorrect because the user can still describe instances.

Answer

The user cannot describe DB instances.

Answer

The user can modify prod-db because the Allow statement covers it.

Answer

The user cannot modify any DB instance.

Question 7

A database specialist needs to monitor the resource utilization of Amazon RDS DB instances. Which AWS service provides OS-level metrics such as memory, disk, and CPU usage?

Accepted Answer

Amazon RDS Enhanced Monitoring. Option B is correct. Enhanced Monitoring provides OS-level metrics for RDS instances. Option A is wrong because Performance Insights provides database performance metrics, not OS metrics. Option C is wrong because CloudWatch provides hypervisor-level metrics, not OS metrics. Option D is wrong because CloudTrail logs API calls.

Answer

Amazon RDS Performance Insights

Answer

Amazon CloudWatch

Answer

AWS CloudTrail

Question 8

A data engineer is troubleshooting a slow-running query on an Amazon Redshift cluster. The query involves large table joins and aggregations. Which diagnostic step should be taken FIRST to understand the query execution plan and identify bottlenecks?

Accepted Answer

Run the EXPLAIN command on the query to review the execution plan.. Option B is correct because the EXPLAIN command shows the query execution plan, including join types, distribution styles, and sort keys, which helps identify bottlenecks. Option A is incorrect because STL_QUERY logs completed queries but does not provide the plan. Option C is incorrect because SVV_TABLE_INFO gives table statistics, not the query plan. Option D is incorrect because WLM metrics show queue performance, not individual query plans.

Answer

Monitor the WLM queue metrics for the query.

Answer

Check the SVV_TABLE_INFO view for table distribution and sort keys.

Answer

Query the STL_QUERY system table to review the query text.

Question 9

A company runs a production Amazon RDS for PostgreSQL database with automated backups enabled. A database administrator accidentally dropped a critical table. The administrator wants to restore the table from a point in time before the drop. The database is 1 TB in size and the recovery point objective (RPO) is 5 minutes. Which approach minimizes downtime?

Accepted Answer

Use the point-in-time recovery feature to restore the database to a new DB instance at a time before the drop, then use pg_dump to export the table and import it into the production database.. Point-in-time recovery (PITR) to a new DB instance is the most efficient way to restore a specific table without affecting the existing production database. Restoring to the existing instance would cause downtime. pg_dump from a read replica is slower and not point-in-time. Manual backup from S3 is not automated and not point-in-time.

Answer

Restore the automated backup from S3 to a new EC2 instance running PostgreSQL, then export the table and import it into the production database.

Answer

Restore the database from the most recent manual snapshot to a new instance, then use pg_dump to extract the table and import it into the production database.

Answer

Create a read replica from the production database, stop replication, and use pg_dump to extract the table from the replica and import it into the production database.

Question 10

A company is using Amazon RDS for MariaDB. The database administrator wants to monitor the database for slow queries. Which TWO services can be used to achieve this? (Choose TWO.)

Accepted Answer

Amazon RDS Performance Insights. RDS Performance Insights provides a dashboard for database performance and can identify slow queries. RDS Enhanced Monitoring provides OS-level metrics but not query-specific. CloudWatch Logs can capture slow query logs if enabled. CloudTrail logs API calls. AWS Config tracks configuration.

Answer

AWS Config

Answer

Amazon RDS Enhanced Monitoring

Answer

AWS CloudTrail

Question 11

A company is migrating a PostgreSQL database to Amazon Aurora PostgreSQL. The database has a large table that is frequently accessed. The team wants to minimize downtime during the migration. Which TWO strategies should be used together?

Accepted Answer

Use AWS DMS to create a target Aurora DB cluster and replicate data.. Options B and D are correct because using AWS DMS with ongoing replication allows for near-zero downtime migration, and creating an Aurora read replica from a PostgreSQL instance is not possible; instead, DMS is the correct tool. Option A is wrong because taking a snapshot and restoring requires downtime. Option C is wrong because AWS SCT is for schema conversion, not data migration. Option E is wrong because there is no direct replication from PostgreSQL to Aurora without DMS.

Answer

Take a manual snapshot of the source database and restore it to Aurora.

Answer

Use AWS Schema Conversion Tool (AWS SCT) to convert the schema.

Answer

Configure Aurora as a read replica of the PostgreSQL instance.

Question 12

A company has an Amazon RDS for MySQL DB instance with automated backups enabled. The database is 500 GB in size. The company wants to create a new test database from the current state with minimal impact on production. Which approach meets these requirements?

Accepted Answer

Take a snapshot of the DB instance and restore it to a new instance.. Option B is correct because restoring a snapshot to a new instance creates a copy without affecting the source. Option A is wrong because creating a read replica increases load on the source. Option C is wrong because exporting to S3 and re-importing is more complex and slower. Option D is wrong because a manual backup before restore adds overhead.

Answer

Create a read replica and promote it to a standalone instance.

Answer

Use mysqldump to export the database and import into a new instance.

Answer

Create a manual DB snapshot from the automated backup and restore.

Question 13

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. During the migration, they need to ensure minimal downtime. Which AWS service should be used for the migration?

Accepted Answer

AWS Database Migration Service. AWS Database Migration Service (DMS) is designed for minimal-downtime migrations, supporting continuous replication.

Answer

AWS DataSync

Answer

Amazon S3 Transfer Acceleration

Answer

AWS Server Migration Service

Question 14

A company is running a production Amazon RDS for MySQL Multi-AZ DB instance. The database experiences intermittent high latency and the CloudWatch 'ReadLatency' metric spikes during periods of heavy read traffic. The application uses a single database endpoint. What is the MOST effective way to reduce read latency without changing the application code?

Accepted Answer

Enable a Multi-AZ deployment with one or more readable standby replicas.. Option C is correct because enabling Multi-AZ with a read replica allows read traffic to be offloaded to the standby replica, reducing load on the primary and improving read latency, all without application changes. Option A is wrong because increasing instance size may help but is less cost-effective and doesn't specifically target read-heavy workloads. Option B is wrong because enabling Multi-AZ alone does not provide a separate read endpoint. Option D is wrong because Amazon RDS does not support sharding natively without application changes.

Answer

Implement database sharding across multiple RDS instances.

Answer

Enable Multi-AZ on the existing DB instance to provide a standby for failover.

Answer

Increase the DB instance class to a larger size.

Question 15

A company has an Amazon DynamoDB table with on-demand capacity mode. They notice that write requests are being throttled during peak hours. The table has a global secondary index (GSI) that is also throttled. Which action should the database specialist take to resolve the throttling?

Accepted Answer

Review the partition key design and consider adding a suffix to distribute writes more evenly.. Option C is correct because in on-demand mode, throttling can occur if a single partition key receives more than 1,000 WCU or 3,000 RCU. Adjusting the partition key design to spread the workload more evenly can resolve throttling. Option A is wrong because the table is on-demand, so switching to provisioned capacity might not help if the access pattern is uneven. Option B is wrong because the GSI inherits throttling from the base table; adding more GSI capacity is not applicable in on-demand mode. Option D is wrong because DynamoDB Streams do not directly affect throttling.

Answer

Enable DynamoDB Streams to offload write operations.

Answer

Switch to provisioned capacity mode and increase write capacity units (WCU).

Answer

Increase the write capacity of the GSI by updating the table's provisioned throughput.