DBS-C01 Practice Test 11 — 15 Questions

Question 1

Which THREE of the following are best practices for securing an Amazon Aurora MySQL database? (Select THREE.)

Accepted Answer

Enable encryption at rest using AWS KMS.. Options A, B, and D are correct. Enabling encryption at rest with AWS KMS (A) protects data stored on disk. Audit logging (B) tracks database activity for security monitoring. IAM database authentication (D) provides a secure, managed method for access control without storing credentials. Option C is wrong because storing credentials in application code is insecure and violates best practices. Option E is wrong because disabling automated backups reduces data durability and recovery capabilities.

Answer

Store database credentials in application code for simplicity.

Answer

Disable automated backups to reduce attack surface.

Question 2

A company uses Amazon ElastiCache for Redis to cache frequently accessed data. The cache cluster experiences high CPU utilization during peak hours. The cluster has a single node of type cache.r5.large. What is the most cost-effective way to reduce CPU utilization while maintaining performance?

Accepted Answer

Add a read replica to distribute read traffic.. Adding a read replica distributes read traffic away from the primary node, reducing its CPU utilization. This is more cost-effective than upgrading to a larger instance type (option B) because you can add a smaller replica node. Option A (enabling encryption) does not reduce CPU utilization and adds overhead. Option D (changing maxmemory-policy) also does not reduce CPU utilization.

Answer

Enable encryption at rest and in transit.

Answer

Upgrade to a cache.r5.xlarge node type.

Answer

Increase the maxmemory-policy parameter to 'allkeys-lru'.

Question 3

A company uses Amazon RDS for PostgreSQL and needs to ensure that only specific IP addresses can connect to the database. Which configuration should be used?

Accepted Answer

Modify the VPC security group associated with the DB instance to allow inbound traffic only from specific IP addresses.. VPC security groups act as a virtual firewall that controls inbound and outbound traffic to the DB instance. By modifying the security group to allow inbound traffic only from specific IP addresses, you restrict database access to those IPs. Option A is incorrect because DB subnet groups define which subnets the RDS instance can reside in, not IP filtering. Option B is incorrect because the rds.force_ssl parameter enforces SSL connections, not IP restrictions. Option C is incorrect because IAM policies control permissions to AWS API actions, not network-level access to the database.

Answer

Configure the DB subnet group to allow only specific IP addresses.

Answer

Set the rds.force_ssl parameter in the DB parameter group.

Answer

Create an IAM policy that restricts access to the RDS API based on source IP.

Question 4

A company is running an Amazon RDS for MySQL instance as shown in the exhibit. The application is experiencing high write latency. The instance has a high number of write operations and the storage queue depth is consistently above 100. Which change would most effectively reduce write latency?

Accepted Answer

Modify the storage type to Provisioned IOPS (io1) with 3000 IOPS.. The instance is experiencing high write latency with a consistently high storage queue depth (above 100), which indicates that the current storage (likely gp2 or magnetic) cannot keep up with the write IOPS demand. Provisioned IOPS (io1) with 3000 IOPS guarantees a dedicated level of IOPS, reducing queue depth and write latency by ensuring the storage subsystem can handle the write workload without throttling.

Answer

Change the instance class to db.m5.xlarge.

Answer

Enable Multi-AZ to offload writes to a standby.

Answer

Increase the allocated storage to 200 GB.

Question 5

A company is using Amazon DynamoDB for a high-traffic application. Users report occasional 'ProvisionedThroughputExceededException' errors. The application uses consistent reads and retries with exponential backoff. What is the MOST efficient way to handle these errors and reduce the number of retries?

Accepted Answer

Enable DynamoDB Auto Scaling for the table. DynamoDB Auto Scaling adjusts the provisioned throughput automatically in response to traffic patterns, reducing throttling and the need for retries. Option A is wrong because increasing read capacity manually is inefficient and does not adapt to fluctuating traffic. Option B is wrong because switching to eventually consistent reads changes the consistency model, which may not be acceptable for the application's requirements. Option D is wrong because increasing write capacity does not address read throttling.

Answer

Increase the provisioned read capacity units manually

Answer

Switch to eventually consistent reads

Answer

Increase the provisioned write capacity units manually

Question 6

A social media startup is selecting a database for user profiles with a flexible schema and high write throughput. The application is built on Node.js and requires low-latency access. Which database should they choose?

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is the correct choice because it is a fully managed NoSQL key-value and document database that offers flexible schema (schemaless), single-digit millisecond latency at any scale, and is designed for high write throughput. It integrates natively with Node.js via the AWS SDK and supports auto-scaling to handle unpredictable write loads, making it ideal for a social media startup's user profile store.

Answer

Amazon Aurora

Answer

Amazon ElastiCache for Redis

Answer

Amazon RDS for MySQL

Question 7

A social media application stores user posts in a DynamoDB table with a partition key of user_id and a sort key of timestamp. The most frequent query is to retrieve the 10 most recent posts for a given user. Which secondary index design would optimize this query?

Accepted Answer

Create an LSI with user_id as the partition key and timestamp as the sort key.. A Local Secondary Index (LSI) on the base table with the same partition key (user_id) and a sort key of timestamp allows efficient retrieval of the 10 most recent posts for a given user. An LSI shares the same partition key as the base table, so querying by user_id with ScanIndexForward=false and Limit=10 returns the most recent items without needing to replicate data or incur additional write costs.

Answer

Create a GSI with user_id as the partition key and timestamp as the sort key.

Answer

Use DynamoDB Streams to populate an Amazon Elasticsearch cluster for search queries.

Answer

Query the base table using the sort key timestamp with a limit of 10.

Question 8

A database specialist is troubleshooting an Amazon RDS for SQL Server instance that is running out of storage. The instance has 500 GB of provisioned storage and is using General Purpose SSD (gp2). The specialist wants to set up an alarm to notify when free storage space drops below 50 GB. Which CloudWatch metric and threshold should be used?

Accepted Answer

Monitor the 'FreeStorageSpace' metric in bytes and set a threshold of 53687091200.. The correct metric is 'FreeStorageSpace' which is reported in bytes by CloudWatch for Amazon RDS. 50 GB equals 50 × 1024³ = 53,687,091,200 bytes. Therefore, setting a threshold of 53687091200 bytes triggers the alarm when free space drops below 50 GB. Option A is incorrect because 'FreeStorageSpace' is not available in percent; you must use bytes. Option B is incorrect because 'DiskSpaceUtilization' is not a standard CloudWatch metric for RDS (it is used for EC2). Option D is incorrect because although 'FreeStorageSpace' is the right metric, the threshold must be specified in bytes, not gigabytes; CloudWatch does not accept a unit other than bytes for this metric.

Answer

Monitor the 'FreeStorageSpace' metric in percent and set a threshold of 10.

Answer

Monitor the 'DiskSpaceUtilization' metric and set a threshold of 90.

Answer

Monitor the 'FreeStorageSpace' metric in gigabytes and set a threshold of 50.

Question 9

A developer is troubleshooting a slow-running query on an Amazon RDS for PostgreSQL instance. The query is performing a sequential scan on a large table. Which AWS service or feature should the developer use to identify the missing index?

Accepted Answer

Amazon RDS Performance Insights. Amazon RDS Performance Insights provides database performance analysis with a dashboard that helps identify performance bottlenecks, such as missing indexes causing sequential scans. Option A is wrong because Amazon RDS Enhanced Monitoring provides OS-level metrics, not database query details. Option B is wrong because AWS CloudTrail logs API calls to AWS services, not database queries. Option D is wrong because Amazon CloudWatch Logs can store database logs but does not analyze query performance to identify missing indexes.

Answer

Amazon RDS Enhanced Monitoring

Answer

AWS CloudTrail

Answer

Amazon CloudWatch Logs

Question 10

A company is using Amazon Redshift for analytics. The security team wants to audit all SQL queries executed against the database, including the actual query text, for compliance. They also want to ensure that the audit logs are stored in a secure, immutable location. Which THREE services or features should they use together to meet these requirements?

Accepted Answer

Redshift Audit Logging. Options A, C, and E are correct. Redshift Audit Logging captures SQL queries. CloudWatch Logs can be used as a destination for audit logs (via streaming). Then, CloudWatch Logs can export logs to S3, and S3 Object Lock provides immutability. Option B is for performance, not auditing. Option D is for network monitoring.

Answer

VPC Flow Logs

Answer

Redshift Spectrum

Question 11

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle using AWS DMS. The source database is 2 TB and has high transaction volume. The migration needs minimal downtime. Currently, full load completes but CDC task fails with 'ORA-1555: snapshot too old' errors. What should the DBA do to resolve this?

Accepted Answer

Increase the undo retention period and undo tablespace size on the source Oracle database.. The 'ORA-1555: snapshot too old' error occurs when Oracle's undo data for a read-consistent view is overwritten before DMS can read it. Increasing the undo retention period and undo tablespace size on the source database ensures that undo data is preserved longer, allowing DMS's CDC task to read consistent data without errors. Option B is correct because it directly addresses the root cause. Option A would restart the full load but not fix the CDC failure. Option C (supplemental logging and larger DMS instance) does not resolve undo retention issues. Option D (reducing transactions) is not practical and may cause data loss. Therefore, the correct solution is to increase undo retention and tablespace size.

Answer

Restart the migration with a new full load and use a smaller task.

Answer

Enable supplemental logging on the source and use a larger DMS instance.

Answer

Reduce the transaction volume by pausing non-essential transactions during CDC.

Question 12

A financial services company is migrating a 500 GB Oracle database to Amazon Aurora MySQL-Compatible Edition. The migration must have minimal downtime and support bidirectional replication for a test-and-cutover approach. The company currently uses Oracle GoldenGate for replication. Which migration strategy should be used?

Accepted Answer

Use AWS DMS with a full load and ongoing replication from Oracle to Aurora MySQL, then cut over.. AWS DMS with full load and ongoing replication is the correct strategy because it supports minimal-downtime migration from Oracle to Aurora MySQL and can handle bidirectional replication for a test-and-cutover approach. DMS uses change data capture (CDC) from Oracle's redo logs to keep the target in sync, allowing you to validate the target before cutting over. This meets the requirement for minimal downtime and a test-and-cutover workflow without relying on Oracle GoldenGate.

Answer

Use AWS Schema Conversion Tool (SCT) to convert the schema and then use AWS DMS for a one-time full load.

Answer

Use AWS DMS with Oracle GoldenGate as a source for continuous replication to Aurora MySQL.

Answer

Use Oracle GoldenGate to replicate directly to Aurora MySQL, then cut over.

Question 13

A company wants to migrate an on-premises MongoDB database to Amazon DocumentDB. The migration must be performed with minimal downtime and should support live data synchronization. Which AWS service should be used?

Accepted Answer

AWS Database Migration Service (DMS) with ongoing replication.. AWS Database Migration Service (DMS) with ongoing replication is the correct choice because it supports continuous change data capture (CDC) from a source MongoDB database to Amazon DocumentDB, enabling live data synchronization with minimal downtime. DMS can perform a full load followed by ongoing replication using the MongoDB oplog to capture and apply changes in near real-time, which meets the requirement for minimal downtime during migration.

Answer

AWS Glue with streaming ETL jobs.

Answer

AWS Data Pipeline to schedule periodic data loads.

Answer

AWS S3 with AWS Lambda functions to sync data.

Question 14

A company is running an Amazon RDS for MySQL Multi-AZ DB instance. They notice that the application is experiencing increased latency during peak hours. The DB instance's CPU utilization is consistently above 80%, and the Read Latency metric is high. Which action would most effectively reduce the latency without requiring application changes?

Accepted Answer

Create a read replica and direct read queries to it.. Creating a read replica offloads read queries from the primary DB instance, reducing read latency and CPU utilization without requiring application changes. Option B is incorrect because disabling Multi-AZ removes the standby instance, reducing availability and not addressing read latency. Option C is incorrect because increasing the instance class may improve performance but does not specifically offload read traffic; read replicas are more targeted for read-heavy workloads. Option D is incorrect because the instance already has Multi-AZ enabled; enabling it again has no effect and does not reduce read latency.

Answer

Disable Multi-AZ to free up resources.

Answer

Increase the DB instance class to a larger size.

Answer

Enable Multi-AZ on the DB instance.

Question 15

A company runs an Amazon Aurora MySQL database cluster with one writer and two readers. The application suddenly fails with 'Too many connections' error. The writer instance's maximum connections is set to 1000. Which configuration change would best resolve the issue while maintaining high availability?

Accepted Answer

Enable Amazon RDS Proxy for the database cluster.. Amazon RDS Proxy acts as a connection pooler that manages database connections efficiently. By reducing connection churn and reusing connections, it prevents the 'Too many connections' error without overloading the instance. Option B is incorrect because simply increasing max_connections could lead to resource exhaustion and degradation of performance. Option C is incorrect because read replicas cannot accept write traffic; they are read-only. Option D is incorrect because manually killing idle connections is a temporary fix and not a configuration change; it does not prevent the issue from recurring.

Answer

Increase the max_connections parameter on the writer instance to 5000.

Answer

Redirect all write requests to one of the read replicas.

Answer

Manually kill idle connections from the database.