DBS-C01 Practice Exam 61 — 20 Questions

Question 1

Which TWO factors should be considered when choosing between Amazon DynamoDB and Amazon RDS for MySQL for a new e-commerce application with variable traffic patterns?

Accepted Answer

Operational overhead: DynamoDB is serverless, RDS requires patching and provisioning.. DynamoDB is a fully managed serverless service that eliminates the need for patching, provisioning, or managing servers, whereas Amazon RDS for MySQL requires manual patching, scaling, and instance provisioning. This operational overhead difference is critical for variable traffic patterns, as DynamoDB automatically handles infrastructure management, reducing administrative burden.

Answer

Ability to perform complex joins and aggregations: DynamoDB supports SQL-like queries.

Answer

Support for ACID transactions in both databases.

Answer

Encryption at rest is only available for RDS.

Question 2

A company uses Amazon DynamoDB to store session data for a web application. During peak hours, they experience occasional ProvisionedThroughputExceededException errors. The table has a read capacity of 1000 RCU and a write capacity of 500 WCU. The application uses strongly consistent reads. The traffic pattern shows short bursts of reads exceeding 1000 RCU. What is the MOST cost-effective way to handle these bursts without changing the application?

Accepted Answer

Enable DynamoDB Auto Scaling to adjust RCU dynamically. Enabling DynamoDB Auto Scaling (Option A) is the most cost-effective solution because it automatically adjusts read capacity in response to traffic patterns, handling short bursts without manual intervention or over-provisioning. It does not require application changes. Option B is more expensive due to higher static capacity. Option C requires switching to eventually consistent reads, which would change application behavior and may not be acceptable for session data requiring strong consistency. Option D adds cost and complexity with DAX without addressing read capacity limits directly.

Answer

Increase RCU to 2000 and enable Auto Scaling

Answer

Switch to eventually consistent reads

Answer

Use DynamoDB Accelerator (DAX) for caching reads

Question 3

A company runs a PostgreSQL database on Amazon RDS for a CRM application. The database is 500 GB and experiences high read traffic. The company wants to improve read scalability and reduce latency. Which TWO actions should the company take? (Choose two.)

Accepted Answer

Implement Amazon ElastiCache for Redis to cache common queries.. Amazon ElastiCache for Redis can cache the results of frequently executed read queries, offloading read traffic from the RDS PostgreSQL instance and reducing latency for repeated queries. This is especially effective for read-heavy workloads where the same data is requested many times, as Redis provides sub-millisecond response times and reduces the load on the database.

Answer

Store large objects in Amazon S3 and reference them.

Answer

Enable Multi-AZ for automatic failover.

Answer

Migrate data to Amazon DynamoDB with Global Tables.

Question 4

Which TWO steps are required when migrating an on-premises Microsoft SQL Server database to Amazon RDS for SQL Server using AWS DMS with ongoing replication?

Accepted Answer

Enable MS-CDC (change data capture) on the source database.. AWS DMS requires MS-CDC (change data capture) to be enabled on the source SQL Server database when using ongoing replication (change data capture). CDC captures insert, update, and delete activity from the transaction log, allowing DMS to apply those changes to the target RDS for SQL Server instance without requiring full table reloads.

Answer

Create a VPC peering connection between the on-premises network and the DMS VPC.

Answer

Install the DMS agent on the source SQL Server instance.

Answer

Configure MS-Replication on the source database.

Question 5

A company is using Amazon DynamoDB and wants to ensure that all data is automatically encrypted at rest. What is the default encryption status for a new DynamoDB table?

Accepted Answer

Encryption is enabled by default using an AWS-owned key.. All new DynamoDB tables are encrypted at rest by default using an AWS-owned key. Option A is wrong because encryption is not optional; it is always enabled by default. Option B is wrong because encryption is enabled by default, not disabled. Option D is wrong because the default key is AWS-owned, not a customer-managed key.

Answer

Encryption is optional and can be enabled during table creation.

Answer

Encryption is disabled by default and must be enabled manually.

Answer

Encryption is enabled by default using a customer-managed key.

Question 6

A company is investigating a performance issue with an Amazon Aurora MySQL database. The output of the describe-db-instances command is shown. The application experiences intermittent slowdowns during write-heavy periods. Which change would MOST likely improve write performance?

Accepted Answer

Increase the provisioned IOPS to 10000. Increasing provisioned IOPS directly improves write throughput by reducing I/O latency. In this scenario, write-heavy periods cause intermittent slowdowns, which are often due to hitting the IOPS limit of the current instance configuration. Option A is incorrect because Aurora Replicas only offload reads and have no effect on write performance. The writer instance still handles all writes regardless of replicas.

Answer

Add an Aurora Replica to distribute read traffic and reduce load on the writer

Answer

Change StorageType to gp2 and increase AllocatedStorage to 200 GB

Answer

Set StorageEncrypted to false to reduce encryption overhead

Question 7

Arrange the steps to set up cross-Region read replicas for an Amazon Aurora MySQL DB cluster in the correct order.

Accepted Answer

Enable binary logging on the source Aurora MySQL DB cluster, then create a cross-Region read replica in the target Region, then verify replication status.. Cross-Region replicas require binary logging enabled on the source, then creating a read replica in another Region and verifying replication.

Answer

Create a cross-Region read replica in the target Region, then enable binary logging on the source cluster, then verify replication.

Answer

Enable binary logging on the source cluster, then promote the read replica to a standalone cluster, then verify replication.

Answer

Create a read replica in the same Region, then enable cross-Region replication by modifying the source cluster, then verify.

Question 8

A database administrator is creating an IAM policy to allow a DevOps engineer to manage production RDS instances. The policy above is attached to the engineer's IAM role. The engineer reports that they cannot create a new DB instance with the identifier 'prod-analytics'. What is the most likely reason?

Accepted Answer

The engineer does not have permissions to pass an IAM role to the DB instance if one is specified.. The most likely reason is that when creating the DB instance, the engineer specified an IAM role to be associated with the instance (e.g., for backup or monitoring). The attached policy does not include an 'iam:PassRole' action, which is required to pass the role to RDS. Without it, the CreateDBInstance call fails due to insufficient permissions to pass the specified role.

Answer

The policy does not allow the 'rds:CreateDBInstance' action on the required resource because the resource ARN pattern is incorrect.

Answer

The policy does not include the 'rds:CreateDBSecurityGroup' action.

Answer

The policy does not include the 'rds:CreateDBInstance' action for all regions.

Question 9

A company runs a financial analytics platform on Amazon DynamoDB. The table stores transaction records with a partition key of account_id and a sort key of transaction_timestamp. Each account has thousands of transactions. The application frequently queries the most recent transactions for a given account_id, sorted by timestamp in descending order. Recently, as the number of accounts grew, the query latency increased significantly. The DynamoDB table has provisioned read capacity of 10,000 RCUs, and CloudWatch metrics show that consumed read capacity is at 60%. The database specialist suspects that the issue is due to the query pattern. Which action should the database specialist take to reduce query latency?

Accepted Answer

Create a Global Secondary Index (GSI) with account_id as partition key and transaction_timestamp as sort key, and query the GSI with ScanIndexForward set to false.. Creating a Global Secondary Index (GSI) with account_id as the partition key and transaction_timestamp as the sort key allows the application to query the most recent transactions for a given account_id efficiently. By setting ScanIndexForward to false in the query, DynamoDB returns items in descending order by sort key, which directly matches the query pattern. This avoids the need to scan all transactions for an account and then sort them, significantly reducing latency. The existing table's sort key is transaction_timestamp, but the query pattern requires descending order; the GSI provides an optimized access path without changing the base table structure.

Answer

Migrate the table to Amazon Aurora PostgreSQL with a secondary index on account_id and transaction_timestamp.

Answer

Enable DynamoDB Accelerator (DAX) to cache query results.

Answer

Increase the provisioned read capacity to 20,000 RCUs to handle the load.

Question 10

Refer to the exhibit. A developer runs a DynamoDB query against a global secondary index. The index's partition key is 'status' and sort key is 'created_at'. There are many items with status 'PENDING' in the table. Why does the query return zero items?

Accepted Answer

The global secondary index is not yet backfilled with data from the base table.. When a global secondary index (GSI) is created on an existing DynamoDB table, the index is populated asynchronously with data from the base table. If the query returns zero items, it likely means the backfill process has not yet completed, so the index does not yet contain the items that match the query. This is a common scenario when a GSI is newly added and the table contains a large number of items.

Answer

The query is incorrectly targeting the base table instead of the index.

Answer

The query must include a condition on the sort key to return results.

Answer

The key-condition-expression uses the wrong attribute name placeholder.

Question 11

A financial services company uses Amazon DynamoDB to store transaction records. The table has a partition key of 'account_id' and a sort key of 'transaction_time'. Recent queries for a specific account's transactions within a time range are experiencing high latency. The table has read capacity units set to auto-scaling. Which design change would most improve query performance?

Accepted Answer

Create a global secondary index with a different partition key.. Creating a global secondary index (GSI) with a different partition key can distribute read traffic across multiple partitions, avoiding hot partitions caused by frequent access to the same account_id. This improves query performance for time-range queries on a specific account. Option A (changing sort key) would not help if the partition itself is overloaded. Option B (DAX) caches results but does not address hot partitions, and may not help if the queries are not cacheable. Option C (increasing RCUs) may not help if the existing partition is hot due to throttling at the partition level.

Answer

Change the sort key to a composite attribute for better filtering.

Answer

Enable DynamoDB Accelerator (DAX) for the table.

Answer

Increase the read capacity units for the table.

Question 12

A company is using Amazon RDS for MySQL and wants to implement database activity monitoring to detect suspicious queries. Which TWO AWS services can be used together to achieve this?

Accepted Answer

AWS Lambda. Options A and E are correct. Amazon RDS for MySQL can publish database logs (such as general logs, slow query logs, or audit logs) to Amazon CloudWatch Logs. CloudWatch Logs can then trigger an AWS Lambda function to analyze the logs in real-time and detect suspicious queries. Option B (AWS CloudTrail) records API calls made to AWS services, not database queries. Option C (AWS Systems Manager Patch Manager) is used for patching OS and applications. Option D (Amazon Inspector) is a vulnerability assessment service, not for database activity monitoring.

Answer

AWS CloudTrail

Answer

AWS Systems Manager Patch Manager

Answer

Amazon Inspector

Question 13

A media company is storing large video files (up to 10 GB each) in Amazon S3 and needs to maintain metadata about each file, including title, duration, and upload timestamp. The workload involves frequent writes (1000+ per second) and occasional read queries by title. Which database is best suited for this metadata store?

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is the best choice because it supports single-digit millisecond latency at any scale, handles over 1000 writes per second with auto-scaling, and can efficiently serve occasional read queries by title using a global secondary index (GSI) on the title attribute. Its fully managed, serverless nature eliminates operational overhead for high-throughput metadata storage.

Answer

Amazon Neptune

Answer

Amazon RDS for MySQL

Answer

Amazon ElastiCache for Memcached

Question 14

A healthcare application requires storing patient records that include structured data (e.g., name, age) and unstructured data (e.g., medical images). The application needs to query structured data with SQL and serve images via HTTPS. Which combination of AWS services provides the MOST efficient design?

Accepted Answer

Amazon RDS for PostgreSQL for structured data and Amazon S3 for images with Amazon CloudFront. Amazon RDS for PostgreSQL provides full SQL querying capabilities for structured patient data, while Amazon S3 with Amazon CloudFront offers scalable, low-latency HTTPS serving of medical images. CloudFront caches images at edge locations, reducing latency and offloading S3, which is the most efficient design for mixed structured/unstructured workloads.

Answer

Amazon DynamoDB for structured data and Amazon S3 for images with DynamoDB Accelerator (DAX)

Answer

Amazon RDS for MySQL for structured data and Amazon EFS for images

Answer

Amazon Redshift for structured data and Amazon S3 for images

Question 15

Refer to the exhibit. An Amazon RDS for Oracle instance is experiencing ORA-00257 errors. The DBA has already increased the archive log retention setting. What is the most efficient next step to resolve the issue without manual intervention?

Accepted Answer

Modify the DB instance to increase the allocated storage.. The ORA-00257 error indicates the flash recovery area is full. In Amazon RDS for Oracle, the flash recovery area size is tied to the allocated storage (default is 30% of allocated storage). Increasing allocated storage automatically expands the recovery area, resolving the issue without manual intervention. Option A is incorrect because Amazon RDS for Oracle does not support archiving redo logs directly to Amazon S3 as a built-in feature. Option B is incorrect because rebooting the DB instance does not free space in the recovery area; it only restarts the database. Option D is incorrect because manually deleting archive logs using RMAN requires manual intervention, which is not the most efficient automated solution.

Answer

Configure archiving to Amazon S3 to offload logs.

Answer

Reboot the DB instance to clear the recovery area.

Answer

Manually delete old archive logs from the recovery area using RMAN.

Question 16

A company has a MySQL database that stores user profile data. The database is 1 TB and growing. The team wants to archive inactive user profiles that haven't been accessed in over 1 year. The archived data must be queryable but at a slower performance tier. Which approach is most cost-effective?

Accepted Answer

Export inactive profiles to Amazon S3 and use S3 Intelligent-Tiering for storage. The most cost-effective because Amazon S3 with Intelligent-Tiering automatically moves data between access tiers (frequent, infrequent, and archive) based on usage, minimizing storage costs for rarely accessed data. Inactive profiles exported to S3 remain queryable via S3 Select or Athena, meeting the requirement for slower query performance at a fraction of the cost of maintaining a relational database instance.

Answer

Create an RDS read replica and delete inactive records from the primary

Answer

Move inactive profiles to Amazon Aurora Serverless and stop the cluster when not in use

Answer

Use Amazon DynamoDB with TTL to expire inactive profiles

Question 17

A database administrator is trying to delete the RDS instance named 'prod-critical' using the AWS CLI. The IAM policy shown is attached to the user. What will happen?

Accepted Answer

The delete will fail because the Deny statement explicitly denies the action for that resource.. The Deny statement in the policy explicitly denies the 'rds:DeleteDBInstance' action on the resource 'arn:aws:rds:*:*:db:prod-critical'. In AWS IAM, an explicit Deny always overrides any Allow, so the delete will fail. Option A is incorrect because a condition is not relevant; the Deny is unconditional. Option C is incorrect because the policy has no syntax error. Option D is incorrect because the Allow does not apply due to the overriding Deny.

Answer

The delete will succeed only if the user includes a condition.

Answer

The delete will fail because the policy has a syntax error.

Answer

The delete will succeed because the Allow statement grants permission.

Question 18

A company runs a MongoDB workload on Amazon EC2 and wants to migrate to Amazon DocumentDB. The database has a total size of 2 TB and experiences 10,000 writes per second during peak. Which migration strategy minimizes downtime?

Accepted Answer

Use AWS DMS with continuous replication.. AWS DMS with continuous replication (change data capture) is the correct strategy because it allows you to keep the source MongoDB and target DocumentDB synchronized in near-real time, minimizing downtime to a brief cutover window. For a 2 TB database with 10,000 writes per second, a full export/import would take hours and require significant downtime, while DMS handles the initial full load and then continuously applies ongoing changes until you switch over.

Answer

Export data using mongodump and import with mongorestore.

Answer

Use AWS Glue to stream data to DocumentDB.

Answer

Copy data files to Amazon S3 and load into DocumentDB.

Question 19

Refer to the exhibit. An IAM policy is attached to a user who will manage AWS DMS tasks. When the user tries to start a replication task, they receive an access denied error. What is the most likely cause?

Accepted Answer

The policy is missing permissions to describe endpoints and connections. The DMS API requires that a user have permissions to describe endpoints and connections before starting a replication task. Even if the policy grants dms:StartReplicationTask, the service internally calls dms:DescribeEndpoints and dms:DescribeConnections to validate the source and target endpoints. Without those describe permissions, the API call fails with an access denied error, even though the start action itself is allowed.

Answer

The policy does not allow rds:DescribeDBInstances

Answer

The policy does not allow the dms:StartReplicationTask action

Answer

The policy does not allow dms:CreateReplicationTask

Question 20

A company is migrating a 500 GB PostgreSQL database from on-premises to Amazon Aurora PostgreSQL. The migration must have a recovery point objective (RPO) of less than 5 minutes and a recovery time objective (RTO) of less than 30 minutes. Which migration strategy should the company use?

Accepted Answer

Use AWS DMS with full load and ongoing replication.. AWS DMS with full load and ongoing replication is the correct strategy because it supports continuous change data capture (CDC) from the on-premises PostgreSQL source to Amazon Aurora PostgreSQL, enabling an RPO of less than 5 minutes. The full load phase migrates the initial 500 GB, and ongoing replication keeps the target synchronized with minimal lag, while Aurora’s automated failover and fast recovery help achieve an RTO under 30 minutes.

Answer

Create a read replica of the on-premises database and promote it.

Answer

Take a full backup using pg_basebackup and restore to Aurora.

Answer

Use pg_dump to export the database and import into Aurora.