DBS-C01 Mock Exam 92 — 25 Questions

Question 1

A company wants to migrate a 10 GB PostgreSQL database from an on-premises server to Amazon RDS for PostgreSQL. The migration can tolerate several hours of downtime. Which migration method is the MOST straightforward?

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

Accepted Answer

Use pg_dump to export the database and pg_restore to import into RDS. Pg_dump and pg_restore are native PostgreSQL utilities that provide a straightforward, reliable method for migrating a 10 GB database with acceptable downtime. The 10 GB size is well within the practical limits of a logical dump, and the process requires no additional AWS services or complex configuration, making it the simplest approach for a migration that can tolerate several hours of downtime.

Answer

Use AWS Database Migration Service (AWS DMS) with ongoing replication

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Use AWS Schema Conversion Tool (AWS SCT) to migrate the data

Answer

Create an Amazon RDS Read Replica from the on-premises database

Question 2

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 3

A company is deploying a new web application that uses Amazon RDS for MySQL. The application must be highly available across three Availability Zones with automatic failover. Which deployment configuration should be used?

Accepted Answer

Deploy Amazon Aurora MySQL with three Aurora Replicas in different Availability Zones.. Amazon Aurora MySQL is the correct choice because it is designed for high availability across three Availability Zones by default, with six copies of data across three AZs and the ability to create up to 15 Aurora Replicas. The requirement for automatic failover across three AZs is met by deploying three Aurora Replicas in different AZs, ensuring continuous availability even if two AZs fail. Standard Amazon RDS for MySQL Multi-AZ only supports a single standby in one other AZ, not three AZs.

Answer

Deploy Amazon RDS for MySQL in a Single-AZ configuration and use an Application Load Balancer.

Answer

Deploy Amazon RDS for MySQL with Multi-AZ and a standby instance in a different Availability Zone.

Answer

Deploy Amazon RDS for MySQL with Read Replicas in two additional Availability Zones.

Question 4

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 5

A company is using Amazon ElastiCache for Redis to cache frequently accessed data from an RDS MySQL database. The cache hit ratio is currently 85%. The operations team notices that during traffic spikes, the cache eviction rate increases significantly, and the database CPU utilization spikes. The cache cluster uses a single r6g.large node. Which THREE actions should the team take to improve performance? (Choose three.)

Accepted Answer

Add more shards to the cluster to increase total memory.. Adding more shards to the cluster increases the total available memory, which reduces the frequency of evictions during traffic spikes. With more memory, the cache can store more data without forcing out existing entries, thereby maintaining a higher cache hit ratio and reducing the load on the RDS MySQL database.

Answer

Reduce the time-to-live (TTL) for cached items to free up memory faster.

Answer

Configure the cache to use lazy loading only for write-through operations.

Question 6

Match each AWS database-related CLI command to its function.

Accepted Answer

aws rds describe-db-instances: Retrieves details about RDS DB instances. The correct matches pair each AWS CLI command with its corresponding database service. Common confusions involve swapping commands between RDS, DynamoDB, Redshift, and ElastiCache. Remember that each service has its own command namespace (e.g., 'aws rds', 'aws dynamodb', 'aws redshift', 'aws elasticache').

Answer

aws rds describe-db-instances: Retrieves details about DynamoDB tables

Answer

aws dynamodb describe-table: Retrieves details about Redshift clusters

Question 7

A database administrator runs the above AWS CLI command. What is the purpose of the command?

Accepted Answer

Retrieve average number of database connections for mydb.. The AWS CLI command `aws cloudwatch get-metric-statistics` with the namespace `AWS/RDS`, metric name `DatabaseConnections`, and statistic `Average` retrieves the average number of database connections for the specified DB instance `mydb` over the given time period. The `--metric-name DatabaseConnections` parameter explicitly targets the connection count metric, making option B correct.

Answer

Retrieve average free storage space for mydb.

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Retrieve average CPU utilization for mydb.

Answer

Retrieve average write latency for mydb.

Question 8

A company uses a self-hosted MySQL database on EC2. They want to migrate to Amazon RDS for MySQL with minimal downtime and automated failover. Which migration strategy should be used?

Accepted Answer

Set up MySQL replication from EC2 to RDS, then cut over. Setting up MySQL native replication from the EC2-hosted MySQL database to an Amazon RDS for MySQL instance allows for near-zero downtime migration. Once replication is established and lag is minimal, you can simply stop writes on the source, verify replication has caught up, and redirect traffic to the RDS endpoint. This approach also supports automated failover by enabling Multi-AZ on the RDS instance, which provides a synchronous standby replica in a different Availability Zone.

Answer

Use mysqldump to export the database and import to RDS

Answer

Take a snapshot of the EC2 instance and restore to RDS

Answer

Use AWS DMS with full load and CDC

Question 9

A company wants to automate backups for an Amazon RDS for PostgreSQL DB instance. The backup retention period should be 35 days. Which step is required?

Accepted Answer

Enable automated backups with a retention period of 35 days.. Amazon RDS for PostgreSQL supports automated backups with a configurable retention period of up to 35 days. By enabling automated backups and setting the retention period to 35 days, the company meets the requirement without additional tooling or manual effort. Automated backups include transaction logs for point-in-time recovery, which is not available with manual snapshots alone.

Answer

Use AWS Backup to schedule backups.

Answer

Create a manual snapshot every day and delete after 35 days.

Answer

Set up a cross-region snapshot copy.

Question 10

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.. In Amazon RDS for PostgreSQL, the parameter to enforce SSL is 'rds.force_ssl' (often abbreviated as 'force_ssl'). Setting this parameter to 1 in the DB parameter group and rebooting the instance forces all connections to use SSL/TLS. Option A is incorrect because security groups control network access but do not enforce encryption. Option C is incorrect because changing the port only obscures the port number, not enforce encryption. Option D is incorrect because 'require_ssl' is not a valid parameter in RDS PostgreSQL; the correct parameter is 'rds.force_ssl'.

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 11

A company is designing a disaster recovery strategy for an Amazon RDS for PostgreSQL database. They need a Recovery Point Objective (RPO) of less than 5 seconds and a Recovery Time Objective (RTO) of less than 1 minute. Which TWO actions should they take? (Choose two.)

Accepted Answer

Create a cross-region read replica and configure automatic failover using Amazon Route 53 health checks. A cross-region read replica can be promoted to a primary instance in under a minute, and with Amazon Route 53 health checks configured for automatic failover, the DNS update occurs automatically, meeting the RTO of less than 1 minute. The asynchronous replication lag is typically sub-second, achieving an RPO of less than 5 seconds. Option E is correct because a Multi-AZ deployment with a synchronous standby in another Availability Zone provides automatic failover with no data loss (RPO of 0) and failover completes in about 30-60 seconds, satisfying both RPO and RTO requirements.

Answer

Use AWS Database Migration Service for continuous replication to a separate instance

Answer

Create a cross-region read replica and manually update DNS in a disaster

Answer

Take hourly snapshots and restore in another region

Question 12

Arrange the steps to restore an Amazon RDS for MySQL DB instance to a new instance from a manual snapshot in the correct order.

Accepted Answer

Select the manual snapshot from the list, then configure the new DB instance details, then initiate the restore, then wait for the restore to complete.. Restoring from a manual snapshot involves selecting the snapshot, configuring the new instance, and waiting for completion.

Answer

Configure the new DB instance details, then select the manual snapshot from the list, then initiate the restore, then wait for the restore to complete.

Answer

Select the manual snapshot from the list, then initiate the restore, then configure the new DB instance details, then wait for the restore to complete.

Answer

Wait for the restore to complete, then select the manual snapshot from the list, then configure the new DB instance details, then initiate the restore.

Question 13

A database administrator runs the described command. What does the output indicate about the RDS instance?

Accepted Answer

The DB instance is not encrypted at rest.. The output shows 'StorageEncrypted: false' and 'KmsKeyId: null', which indicates the DB instance is not encrypted at rest. Option B is incorrect because the output does not indicate any failed state; it's a valid status showing encryption configuration. Option C is incorrect because the output does not mention the database engine type. Option D is incorrect because an encrypted instance would show 'StorageEncrypted: true' and a non-null KmsKeyId.

Answer

The DB instance is in a failed state.

Answer

The DB instance is running PostgreSQL.

Answer

The DB instance is encrypted at rest using a KMS key.

Question 14

A company needs a fully managed graph database for a social networking application that requires real-time recommendations based on friend connections. Which AWS service should they use?

Accepted Answer

Amazon Neptune. Amazon Neptune is the correct choice because it 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 social networking applications that require real-time friend-of-friend recommendations and traversal queries across complex relationships.

Answer

Amazon DocumentDB

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Amazon ElastiCache

Answer

Amazon DynamoDB

Question 15

A company is using an Amazon RDS for SQL Server database with Multi-AZ deployment. They need to migrate to Amazon RDS for SQL Server in a different AWS region. The database is 1 TB and cannot tolerate more than 15 minutes of downtime. Which strategy minimizes downtime?

Accepted Answer

Set up cross-region replication using native SQL Server log shipping or DMS with ongoing replication, then perform a DNS cutover to the target instance.. It combines native SQL Server log shipping or AWS DMS with ongoing replication to keep the target region instance nearly synchronized with the source, enabling a DNS cutover with minimal downtime. This approach meets the 15-minute downtime requirement by allowing a controlled final sync and cutover, unlike snapshot restore or full-load-only methods that require longer outages. Multi-AZ deployment does not prevent cross-region replication, and log shipping or DMS can handle the 1 TB database within the downtime window if properly configured.

Answer

Create a cross-region read replica in the target region and promote it to a standalone instance.

Answer

Take a snapshot of the source RDS instance and restore it in the target region. Then update the application connection string.

Answer

Use AWS DMS to perform a full load to a new RDS instance in the target region. During the final sync, stop the source and resume from the target.

Question 16

A company is deploying a MySQL RDS instance using this CloudFormation template. After deployment, they notice that the database is not automatically backed up at the scheduled time. What is the most likely cause?

Accepted Answer

The BackupRetentionPeriod must be greater than 0 to enable automated backups; however, it is set to 7, so this is not the issue. The actual cause might be that the DB instance is using a storage engine not supported for backups (e.g., MyISAM).. The BackupRetentionPeriod is set to 7, which is greater than 0, so automated backups are enabled. However, the most likely cause of the backup failure is that the DB instance is using a storage engine like MyISAM, which does not support point-in-time recovery or consistent automated backups in Amazon RDS. RDS automated backups rely on the InnoDB storage engine for crash recovery and transaction consistency; MyISAM tables can cause backup failures or incomplete backups.

Answer

The storage type gp2 does not support automated backups.

Answer

The PreferredBackupWindow is not defined, so backups are disabled.

Answer

MultiAZ is enabled, which disables automated backups.

Question 17

A company is running a PostgreSQL database on Amazon RDS. They need to improve read performance for a reporting application that runs complex queries. The reporting application can tolerate slightly stale data. Which THREE actions should they take? (Choose three.)

Accepted Answer

Modify the DB parameter group to optimize settings for reporting workloads, such as increasing shared_buffers and work_mem.. Modifying the DB parameter group to increase shared_buffers and work_mem can significantly improve the performance of complex reporting queries by allowing more data to be cached in memory and larger sort operations to be performed in memory rather than on disk. Option B is correct because upgrading to a larger instance class with more vCPUs and memory directly addresses the compute and memory demands of complex queries, reducing query execution time. Option C is correct because creating read replicas offloads reporting traffic from the primary database, and since the reporting application can tolerate slightly stale data, the asynchronous replication lag is acceptable.

Answer

Enable Multi-AZ on the RDS instance.

Answer

Implement an Amazon ElastiCache cluster to cache query results.

Question 18

A DBA sees the above error log entries for an Amazon RDS for PostgreSQL DB instance. What is the most likely cause?

Accepted Answer

The user 'myuser@mycompany.com' is using an incorrect password.. The error log entry shows authentication failure for user 'myuser@mycompany.com' with message 'password authentication failed for user'. In PostgreSQL, this specific error indicates the client provided an incorrect password for an existing user. The log does not show any connection limit exceeded or network timeout messages, and the user is referenced by name, confirming the user exists.

Answer

There is a network connectivity issue between the client and the database.

Answer

The database has reached its maximum number of connections.

Answer

The user 'myuser@mycompany.com' does not exist in the database.

Question 19

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database has a large table with a BLOB column storing PDF files. Which migration approach minimizes downtime?

Accepted Answer

Use AWS Database Migration Service (DMS) with ongoing replication.. AWS DMS with ongoing replication (change data capture) allows you to perform an initial full load of the database while continuously capturing and applying changes from the source Oracle database to the target RDS for Oracle instance. This minimizes downtime because you can cut over to the new database after the initial load and replication lag is near zero, rather than taking the source offline for the entire migration.

Answer

Use Oracle Data Pump to export the table and import into RDS.

Answer

Use Oracle RMAN to back up the database and restore to RDS.

Answer

Export the table without the BLOB column, then import the BLOBs separately.

Question 20

Refer to the exhibit. A developer created a DynamoDB table 'UserSessions' with a simple primary key. The application needs to query by user_id as well. What design change should the developer make to support this query efficiently?

Accepted Answer

Create a Global Secondary Index on user_id. A Global Secondary Index (GSI) on user_id allows efficient querying by user_id without altering the base table's primary key structure. The base table uses a simple primary key (likely session_id), and a GSI provides a separate index with its own partition key (user_id) to support non-key attribute queries with eventual consistency, enabling the application to query by user_id efficiently without scanning the entire table.

Answer

Use a Scan operation with a filter

Answer

Add a sort key to the table

Answer

Create a Local Secondary Index on user_id