DBS-C01 Practice Test 30 — 15 Questions

Question 1

A company is migrating a 2 TB PostgreSQL database from on-premises to Amazon RDS for PostgreSQL. The migration must have minimal downtime and support ongoing replication. Which AWS service should be used for the migration?

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

Accepted Answer

AWS Database Migration Service (DMS) with change data capture. AWS Database Migration Service (DMS) with change data capture (CDC) is the correct choice because it supports ongoing replication from the source PostgreSQL database to Amazon RDS for PostgreSQL with minimal downtime. DMS performs a full load of the 2 TB database and then continuously applies changes using PostgreSQL's logical replication slots (via the pglogical extension or native WAL-based CDC), ensuring the target remains synchronized during the migration cutover.

Answer

AWS S3 Transfer Acceleration for direct database export

Answer

AWS Data Migration Service with AWS Glue

Answer

AWS Snowball Edge for offline data transfer

Question 2

A company is using Amazon DynamoDB with global tables (multi-region) for a gaming application. The application writes to a table in us-east-1 and reads from a table in eu-west-1. The team notices that writes in us-east-1 are taking longer than expected to propagate to eu-west-1. What is the most likely cause?

Accepted Answer

Network latency between the regions is causing replication delay. DynamoDB global tables use asynchronous replication across regions, and network latency between regions is the primary factor causing delays in propagation. Option B is incorrect because read and write capacity is independent per region; insufficient capacity in eu-west-1 does not affect replication speed from us-east-1. Option C is incorrect while conflict resolution can occur with concurrent writes, it does not inherently cause delays; replication delay is due to network latency. Option D is incorrect because DynamoDB Streams are required for global tables to function; if they were disabled, replication would not occur at all, not just be delayed.

Answer

The write capacity in eu-west-1 is insufficient

Answer

Conflicts are being resolved due to concurrent writes

Answer

DynamoDB Streams is disabled on the table

Question 3

A database administrator needs to monitor the number of connections to an Amazon RDS for MySQL DB instance. Which Amazon CloudWatch metric should be used?

Accepted Answer

DatabaseConnections. The DatabaseConnections metric in CloudWatch shows the number of current connections to the DB instance.

Answer

NetworkThroughput

Answer

ConnectionAttempts

Answer

ActiveTransactions

Question 4

Which THREE of the following are best practices for managing Amazon DynamoDB tables with provisioned throughput?

Accepted Answer

Use a composite key design with a sort key to enable efficient querying.. Options C, D, and E are correct. Option A is incorrect because creating a global secondary index on every attribute incurs additional costs and storage, and not every query pattern requires an index; GSIs should be designed based on actual access patterns. Option B is incorrect because DynamoDB automatically manages partitions; manual partition splitting is not supported. Option C is correct because a composite key design (partition key and sort key) enables efficient querying using the sort key for filtering and sorting. Option D is correct because DynamoDB Auto Scaling automatically adjusts read/write capacity based on actual traffic, helping to maintain performance without manual intervention. Option E is correct because DynamoDB Accelerator (DAX) provides in-memory caching for frequently accessed items, reducing read latency and improving performance.

Answer

Create a global secondary index on every attribute to support any query pattern.

Answer

Split hot partitions manually to distribute write traffic.

Question 5

A company uses Amazon Aurora MySQL-Compatible Edition. The database specialist notices that the DB cluster's failover time is longer than expected. The primary instance is using a db.r5.large instance class. Which change would most likely reduce the failover time?

Accepted Answer

Use a larger instance class for the Aurora Replicas.. Using a larger instance class for Aurora replicas ensures they can handle the workload after failover, potentially reducing failover time. However, the key factor is that Aurora failover is typically fast, but if replicas are undersized, the time to promote and become fully operational increases. Using a larger instance class for the replicas (or all instances) can help.

Answer

Enable Backtrack on the DB cluster.

Answer

Increase the number of Aurora Replicas.

Answer

Enable Multi-AZ deployment for the DB cluster.

Question 6

A database administrator needs to track changes to an Amazon RDS DB instance's configuration, such as modifications to the DB instance class or security group. Which AWS service should be used?

Accepted Answer

AWS Config. AWS Config records configuration changes to RDS instances. Option A is wrong because CloudWatch Logs are for log data, not configuration changes. Option C is wrong because CloudTrail records API calls, not configuration state. Option D is wrong because Systems Manager Patch Manager is for patching.

Answer

Amazon CloudWatch Logs

Answer

AWS CloudTrail

Answer

AWS Systems Manager Patch Manager

Question 7

A database administrator sees the above error logs in CloudWatch for an Amazon RDS for PostgreSQL DB instance. The application team confirms that the password for 'app_user' is correct. What is the most likely cause of the authentication failures?

Accepted Answer

The host '10.0.1.50' is not listed in the pg_hba.conf file.. The errors show authentication failures from a specific host. If the password is correct, the most likely cause is that the host is not allowed by the pg_hba.conf configuration. RDS for PostgreSQL uses DB parameter groups to control pg_hba.conf rules; the rds.force_ssl parameter or the pg_hba.conf entries may not include that host.

Answer

The password has expired for 'app_user'.

Answer

The user 'app_user' does not have the LOGIN privilege.

Answer

The database is in read-only mode.

Question 8

A company manages multiple RDS for PostgreSQL instances in different AWS accounts. The security team requires that all DB instances have automated backups enabled with a retention period of at least 14 days. How can the company enforce this policy across all accounts?

Accepted Answer

Use AWS Config rules to evaluate and auto-remediate non-compliant instances.. AWS Config with managed rules can evaluate RDS instances and enforce backup settings. Option A is wrong because CloudTrail only logs API calls for auditing, it does not enforce configuration. Option B is wrong because Service Control Policies (SCPs) restrict permissions at the organization level but cannot directly require backup retention on resources. Option C is wrong because IAM policies can control permissions to create instances but cannot enforce backup retention settings on existing instances; they can deny creation if certain conditions are not met, but that is not as comprehensive as AWS Config auto-remediation.

Answer

Use AWS CloudTrail to monitor backup settings and alert on non-compliance.

Answer

Apply a service control policy (SCP) that requires backup retention.

Answer

Create an IAM policy that denies creating DB instances without backup retention.

Question 9

A company runs a critical application on an Amazon RDS for MySQL DB instance. The company requires that the database be available with minimal downtime during a disaster recovery scenario. The current RDS instance is in us-east-1. The company wants to have a standby database in us-west-2 with automatic failover. What should the company do to meet this requirement?

Accepted Answer

Create a cross-region read replica in us-west-2. Configure automatic failover using Amazon Route 53 health checks.. An RDS cross-region read replica can be promoted to a standalone instance in a disaster, providing automatic failover with minimal downtime when combined with Route 53 health checks. Option A (Multi-AZ in us-west-2) does not provide cross-region failover; Multi-AZ only provides high availability within a single region. Option B (snapshots) requires manual restoration and incurs downtime. Option D (Multi-AZ in us-east-1) only protects against Availability Zone failures within us-east-1, not region failures. Therefore, option C is the correct solution.

Answer

Create a Multi-AZ deployment in us-west-2 and use Amazon Route 53 to failover.

Answer

Take daily snapshots and copy them to us-west-2. Restore from snapshot in us-west-2 during a disaster.

Answer

Create a Multi-AZ deployment in us-east-1.

Question 10

A company is using Amazon Redshift for data warehousing. The database administrator needs to optimize query performance. Which TWO actions should the administrator take? (Choose TWO.)

Accepted Answer

Analyze the tables to update statistics for the query optimizer.. Options B and E are correct. Analyzing tables updates statistics for the query optimizer, enabling efficient query plan generation. Running VACUUM reclaims space and re-sorts data, improving data distribution and query performance. Option A is incorrect because increasing nodes is a scaling action, not an optimization action, and adds cost. Option C is incorrect because enabling encryption does not directly impact query performance. Option D is incorrect because disabling compression increases storage and I/O, degrading performance.

Answer

Increase the number of nodes in the cluster.

Answer

Enable encryption for the cluster.

Answer

Disable compression on the tables to reduce CPU overhead.

Question 11

A company is using Amazon RDS for PostgreSQL with read replicas to offload read traffic. The company wants to ensure that the read replicas are always in sync with the primary instance. Which metric should the company monitor to detect replication lag?

Accepted Answer

ReplicaLag. The correct metric to monitor for replication lag in Amazon RDS for PostgreSQL read replicas is ReplicaLag. This metric is available in CloudWatch and directly indicates the time difference between the primary instance and the read replica. Option A (DiskQueueDepth) measures the number of pending I/O requests, not replication lag. Option C (TransactionLogsDiskUsage) measures the amount of transaction logs, which is related but not a direct lag metric. Option D (ReadLatency) measures the latency of read operations, not the synchronization delay.

Answer

DiskQueueDepth

Answer

TransactionLogsDiskUsage

Answer

ReadLatency

Question 12

A company is deploying an Amazon Aurora MySQL database. The company requires that the database withstand the loss of two copies of data without impacting write availability. Which configuration should the company use?

Accepted Answer

Aurora with 6 copies of data across 3 Availability Zones. Aurora MySQL stores 6 copies of data across 3 Availability Zones. The database can withstand the loss of up to two copies without affecting write availability, provided the copies are distributed across AZs. Option D (6 copies across 3 AZs) is correct. Option A (3 copies in 3 AZs) is incorrect because Aurora uses 6 copies, not 3. Option B (2 copies in 2 AZs) provides insufficient redundancy. Option C (3 copies in 2 AZs) is not the architecture; Aurora uses 6 copies across 3 AZs.

Answer

Aurora with 3 copies of data in 3 Availability Zones

Answer

Aurora with 2 copies of data in 2 Availability Zones

Answer

Aurora with 3 copies of data in 2 Availability Zones

Question 13

A company is using Amazon RDS for MySQL with Multi-AZ deployment. The DBA receives an alert that the standby replica is lagging behind the primary. Which TWO actions should the DBA take to investigate the issue? (Choose TWO.)

Accepted Answer

Verify network latency between the primary and standby.. The correct answers are B and C. In Amazon RDS Multi-AZ deployments, the standby replica is synchronously replicated from the primary, and the 'ReplicaLag' metric in CloudWatch is used to monitor the replication delay. Checking this metric (option C) helps identify lag. Additionally, verifying network latency between the primary and standby (option B) can uncover connectivity issues causing lag. Option A is incorrect because Multi-AZ does not have read replicas; Read Replicas are separate from the Multi-AZ standby. Option D is incorrect because storage size does not directly affect replication lag. Option E is incorrect because Multi-AZ uses synchronous replication, and changing to asynchronous would not solve the issue and is not a supported change for Multi-AZ.

Answer

Check the 'Replica Lag' metric for any read replicas.

Answer

Increase the allocated storage to improve IOPS.

Answer

Change the replication type from asynchronous to synchronous.

Question 14

A company is using Amazon DynamoDB with auto scaling enabled. The table's write capacity is set to a minimum of 50 and maximum of 500 write capacity units (WCUs). The actual consumed write capacity is consistently at 100 WCUs. What should the database specialist do to optimize costs without impacting performance?

Accepted Answer

Lower the minimum write capacity to 100 WCUs.. Lower the minimum write capacity to 100 WCUs. With auto scaling enabled and actual consumed write capacity consistently at 100 WCUs, the minimum should match the actual usage to avoid over-provisioning. Setting it to 100 WCUs ensures that baseline capacity is just enough for normal operations, while auto scaling can still scale up to 500 WCUs during traffic spikes. Option A (increasing minimum to 200 WCUs) would raise costs without benefit. Option B (disabling auto scaling and fixing at 100 WCUs) removes the ability to scale up, risking throttling during spikes. Option D (decreasing maximum to 200 WCUs) limits scalability and could cause throttling if traffic exceeds 200 WCUs.

Answer

Increase the minimum write capacity to 200 WCUs.

Answer

Disable auto scaling and set the write capacity to 100 WCUs.

Answer

Decrease the maximum write capacity to 200 WCUs.

Question 15

A company is running an Amazon RDS for MySQL Multi-AZ DB instance. They notice increased latency during peak hours. The DB instance type is db.r5.large, and the storage is General Purpose SSD (gp2) with 500 GB. The application is read-heavy with frequent SELECT queries. Which action would most likely resolve the latency issue without changing the DB instance class?

Accepted Answer

Create an Amazon RDS read replica in the same region.. Adding a read replica offloads read traffic from the primary instance, reducing latency. Option A is wrong because enabling Performance Insights is for monitoring and analysis, not directly improving performance. Option C is wrong because Multi-AZ is for high availability, not read scaling. Option D is wrong because increasing storage size may improve IOPS but does not directly address the read load.

Answer

Enable Performance Insights and analyze queries.

Answer

Enable Multi-AZ on the existing DB instance.

Answer

Increase the allocated storage to 1,000 GB.