DBS-C01 Practice Test 44 — 15 Questions

Question 1

A company uses Amazon DynamoDB with on-demand capacity mode for a critical application. During a marketing campaign, the application experienced throttled requests despite the on-demand mode. The table has a single partition key. The database specialist notices that the throttling occurs sporadically even though overall traffic is within limits. What is the most likely cause?

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

Accepted Answer

The table's partition key is causing a hot partition, leading to throttling on that partition.. On-demand mode accommodates traffic spikes, but if a single partition key is used, all traffic goes to one partition. DynamoDB partitions data by partition key; a single hot key can throttle requests even if overall throughput is within limits. Provisioned capacity is not used. Auto scaling is not relevant. The partition limit is a hard limit.

Answer

The table's provisioned capacity is set too low.

Answer

The table's auto scaling is not configured correctly.

Answer

The application is exceeding the DynamoDB account-level throughput limits.

Question 2

A healthcare company runs an Amazon Aurora MySQL cluster for a patient portal. Read traffic from a reporting service has grown and now causes the writer instance to show high CPU. The reporting queries are read-only and tolerate up to two seconds of replication lag. The company wants to offload reporting without changing application connection strings for the primary writer. Which approach meets these requirements with the least operational overhead?

Accepted Answer

Create an Aurora Replica and configure the reporting service to connect to the reader endpoint of the cluster.. Adding an Aurora Replica and using the cluster's reader endpoint offloads read-only reporting from the writer while keeping application writer connections unchanged. Aurora Replicas share the same storage volume and replicate asynchronously, so the two-second lag budget is satisfied. This scales reads horizontally with far less effort than cross-Region or snapshot-based alternatives.

Answer

Restore a snapshot of the cluster into a new Aurora cluster and run reporting queries against the restored cluster.

Answer

Enable Aurora Global Database and point the reporting service at the secondary Region cluster endpoint.

Answer

Increase the instance class of the writer instance and direct all reporting queries to the cluster endpoint.

Question 3

A company is migrating a 3 TB MySQL database to Amazon Aurora MySQL. They need to validate data consistency after migration. Which approach should they use?

Accepted Answer

Use AWS DMS data validation feature.. AWS DMS data validation feature is the correct approach because it automatically compares source and target records by computing checksums at the table level, ensuring end-to-end consistency without manual intervention. For a 3 TB migration, this built-in feature handles large-scale validation efficiently by validating ongoing replication and full-load data, which is critical for MySQL to Aurora MySQL migrations.

Answer

Compare row counts between source and target tables.

Answer

Run random SELECT queries on a subset of rows to compare values.

Answer

Compute MD5 checksums of the entire dataset in both databases.

Question 4

Refer to the exhibit. A database administrator runs the AWS CLI command and gets the following output: {"Engine":"mysql","DBInstanceStatus":"available","MultiAZ":true,"SecondaryAvailabilityZone":"us-east-1b"}. What can be concluded about the database deployment?

Accepted Answer

The database is a Multi-AZ deployment with a standby in a different Availability Zone.. The output shows `"MultiAZ":true` and `"SecondaryAvailabilityZone":"us-east-1b"`, which are explicit indicators of a Multi-AZ deployment for an RDS MySQL instance. In a Multi-AZ deployment, Amazon RDS automatically provisions and maintains a synchronous standby replica in a different Availability Zone, and the `SecondaryAvailabilityZone` field confirms the standby's location. This matches option D exactly.

Answer

The database is a Single-AZ deployment.

Answer

The database has a Read Replica in a different Availability Zone.

Answer

The database is an Amazon Aurora cluster.

Question 5

A company needs to store session data for millions of users with sub-millisecond latency. The data is key-value in nature and can tolerate eventual consistency. Which database service is best suited?

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is the best choice because it is a fully managed NoSQL key-value and document database designed for single-digit millisecond latency at any scale, making it ideal for session data storage. It supports eventual consistency, which is acceptable for this use case, and can handle millions of users with sub-millisecond read and write performance using its SSD-backed storage and distributed architecture.

Answer

Amazon Redshift

Answer

Amazon Neptune

Answer

Amazon RDS for MySQL

Question 6

A company uses Amazon RDS for PostgreSQL for its e-commerce platform. The application team reports increasing read latency on the primary instance during sales events. Which action should be taken to reduce read load on the primary?

Accepted Answer

Create one or more read replicas. Creating one or more read replicas offloads read traffic from the primary RDS for PostgreSQL instance, directly addressing the increased read latency during sales events. Read replicas are asynchronous replicas that can serve SELECT queries, reducing the load on the primary without requiring application changes to the write path. This is the standard AWS solution for scaling read-heavy workloads in RDS.

Answer

Enable Multi-AZ deployment

Answer

Migrate to Amazon DynamoDB

Answer

Increase the instance size of the primary

Question 7

A database administrator is troubleshooting an Amazon RDS for SQL Server instance that is experiencing high 'ReadIOPS' and 'ReadLatency'. The instance uses General Purpose SSD (gp2) storage. The 'BurstBalance' metric is 0%. What should the administrator do to improve performance?

Accepted Answer

Increase the allocated storage or switch to Provisioned IOPS. The BurstBalance metric at 0% indicates that the gp2 volume has exhausted its burst credits, causing high ReadIOPS and ReadLatency. To improve performance, the administrator should either increase the allocated storage (which increases baseline IOPS for gp2) or switch to Provisioned IOPS (io1/io2) storage, which provides dedicated IOPS regardless of burst credits. This directly addresses the root cause of the performance degradation.

Answer

Enable Multi-AZ to distribute the load

Answer

Create a read replica to offload read traffic

Answer

Disable automatic backups to reduce I/O

Question 8

A company has a critical application that uses Amazon RDS for MySQL with Multi-AZ deployment. During a recent failure, the automatic failover took 2 minutes, causing application timeout. The company needs to reduce failover time to under 30 seconds. Which solution should the database specialist recommend?

Accepted Answer

Migrate the database to Amazon Aurora MySQL.. Amazon Aurora MySQL is designed to reduce failover time significantly compared to standard RDS MySQL Multi-AZ. Aurora typically completes failover in under 30 seconds by using a shared distributed storage volume across multiple Availability Zones, allowing the primary instance to fail over to a read replica without the need to replay redo logs or perform crash recovery. This meets the requirement of reducing failover time to under 30 seconds.

Answer

Create a read replica and promote it during failover.

Answer

Increase the DB instance class to a larger size.

Answer

Implement Amazon RDS Proxy to handle connection draining.

Question 9

Arrange the steps to configure a read replica for an Amazon RDS for PostgreSQL DB instance in a different AWS Region in the correct order.

Accepted Answer

Enable automatic backups on the source DB instance, then create a cross-Region read replica in the target Region, then monitor replication lag.. Cross-Region read replicas require backups enabled on the source, then creating a replica in another Region and monitoring lag.

Answer

Create a cross-Region read replica in the target Region, then enable automatic backups on the source DB instance, then monitor replication lag.

Answer

Monitor replication lag, then enable automatic backups on the source DB instance, then create a cross-Region read replica in the target Region.

Answer

Enable automatic backups on the source DB instance, then monitor replication lag, then create a cross-Region read replica in the target Region.

Question 10

Arrange the steps to switch over from a primary Amazon RDS for Oracle DB instance to a standby in a Multi-AZ deployment (planned failover) in the correct order.

Accepted Answer

First verify the standby replica is healthy and in sync, then initiate the failover using the AWS Management Console or CLI, and finally confirm that the new primary is accepting connections.. Planned failover involves verifying standby health, initiating failover, and confirming connectivity.

Answer

First initiate the failover, then verify the standby replica is healthy and in sync, and finally confirm that the new primary is accepting connections.

Answer

First confirm that the new primary is accepting connections, then verify the standby replica is healthy and in sync, and finally initiate the failover.

Answer

First verify the standby replica is healthy and in sync, then confirm that the new primary is accepting connections, and finally initiate the failover.

Question 11

A company runs an Amazon RDS for Oracle DB instance in a private subnet. The security team wants to allow only the application servers in a specific VPC security group to connect to the database on port 1521, and to block all other traffic. What is the correct way to configure this?

Accepted Answer

Modify the RDS DB instance's security group to allow inbound traffic on port 1521 from the application servers' security group.. Network access to an RDS DB instance is controlled by VPC security groups. To allow only specific application servers, you add an inbound rule to the RDS instance's security group that references the application servers' security group as the source on the database port. Network ACLs, parameter groups, and IAM policies do not provide this level of precise, dynamic network control.

Answer

Create a network ACL on the DB subnet that allows inbound traffic on port 1521 from the application servers' IP addresses.

Answer

Attach an IAM policy to the RDS instance that allows connections only from the application servers' IAM roles.

Answer

Configure the RDS instance's parameter group to restrict connections to specific IP addresses on port 1521.

Question 12

An administrator needs to migrate an on-premises MongoDB database to Amazon DocumentDB. The migration must have near-zero downtime. Which approach should the administrator use?

Accepted Answer

Use AWS DMS with MongoDB as source and DocumentDB as target. AWS DMS supports ongoing replication (change data capture) from MongoDB to Amazon DocumentDB, enabling near-zero downtime migrations by keeping the target synchronized with the source until cutover. This approach avoids the downtime required by offline methods like mongodump/mongorestore or bulk data transfer tools.

Answer

Use AWS DataSync to transfer the MongoDB data files

Answer

Use AWS Glue to extract and load data

Answer

Use mongodump to export and mongorestore to import

Question 13

A company is migrating an on-premises Oracle database to Amazon Aurora PostgreSQL. The database is 1 TB and has complex stored procedures. The migration must be completed within a 4-hour downtime window. Which migration approach is most efficient?

Accepted Answer

Use AWS SCT to convert schema and code, then AWS DMS for data migration.. AWS SCT converts the Oracle schema and complex stored procedures to Aurora PostgreSQL-compatible code, while AWS DMS performs the full data migration within the 4-hour window. This combination handles both schema/code conversion and bulk data transfer efficiently, meeting the time constraint.

Answer

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

Answer

Use Oracle Data Pump to export and pg_restore to import.

Answer

Use AWS DMS with ongoing replication.

Question 14

A company is using Amazon RDS for PostgreSQL. The security team wants to ensure that all connections to the database are encrypted in transit. Currently, applications connect using the PostgreSQL native encryption (SSL/TLS). What is the MOST secure way to enforce encrypted connections?

Accepted Answer

Enable the 'rds.force_ssl' parameter in the DB parameter group and restart the instance.. The rds.force_ssl parameter, when set to 1 in a custom DB parameter group and applied with a reboot, makes the PostgreSQL engine reject any non-SSL connection at the server level. This enforces encryption in transit regardless of client configuration, which is the most secure and reliable enforcement mechanism. It is the documented RDS approach for PostgreSQL and works uniformly for all connecting applications.

Answer

Configure the security group to only allow traffic on port 5432 from trusted IP addresses.

Answer

Use a custom database port that is not commonly used, such as 5433, to avoid unencrypted traffic.

Answer

Modify the DB parameter group to set 'ssl' to 'on' and 'require_ssl' to 'on', then reboot the instance.

Question 15

A company wants to deploy a MySQL database that automatically scales read capacity based on traffic without manual intervention. Which AWS database offering should they use?

Accepted Answer

Amazon Aurora with Auto Scaling for read replicas. Amazon Aurora with Auto Scaling for read replicas is correct because it automatically adjusts the number of Aurora Replicas based on changes in read workload, scaling read capacity without manual intervention. Aurora's Auto Scaling monitors the average CPU utilization or connections of the reader fleet and adds or removes replicas to maintain a target metric, providing seamless read scaling for MySQL-compatible databases.

Answer

Amazon DynamoDB with auto scaling

Answer

Amazon RDS for MySQL with Multi-AZ deployment

Answer

Amazon RDS for MySQL with a Single-AZ deployment