DBS-C01 Practice Test 2 — 10 Questions

Question 1

A company uses Amazon RDS for PostgreSQL to store sensor data. Each sensor sends a row every second. The table has grown to 500 GB and queries filtering on a timestamp column are slow even with an index. The team wants to improve query performance while keeping the data online. Which approach should they take?

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

Accepted Answer

Partition the table by time using PostgreSQL table partitioning. PostgreSQL table partitioning by time (e.g., by day or month) allows the query planner to prune partitions that do not match the timestamp filter, drastically reducing the amount of data scanned. This is the most effective approach for time-series data because it maintains online access and improves query performance without requiring a migration or additional replicas.

Answer

Migrate to Amazon Aurora PostgreSQL and enable parallel query

Answer

Add more indexes on the timestamp column

Answer

Create a read replica and direct queries to the replica

Question 2

A company is migrating a MySQL database from on-premises to Amazon RDS for MySQL. They want to use native MySQL replication to minimize downtime. Which configuration is required in the on-premises MySQL server?

Accepted Answer

Enable binary logging with binlog_format = ROW. Native MySQL replication requires binary logging on the source server to capture all changes. Setting binlog_format = ROW ensures that row-level changes are logged, which is the recommended format for cross-version replication and is required by Amazon RDS for MySQL to support replication from an external source. Without binary logging enabled, the on-premises MySQL server cannot act as a replication master.

Answer

Enable the slow query log

Answer

Enable the audit log

Answer

Enable the error log

Question 3

An e-commerce platform uses Amazon DynamoDB for a shopping cart table with partition key 'user_id' and sort key 'product_id'. The table experiences throttled write requests during flash sales. The access pattern includes reading the entire cart at checkout. Which design change would improve write performance without changing the read pattern?

Accepted Answer

Enable DynamoDB Adaptive Capacity and ensure the table uses on-demand capacity mode. Enabling DynamoDB Adaptive Capacity with on-demand capacity mode automatically scales write capacity to handle traffic spikes during flash sales without requiring manual provisioning. This eliminates throttling while preserving the existing table schema (partition key 'user_id' and sort key 'product_id'), so the read pattern of querying the entire cart by user_id remains unchanged.

Answer

Enable DynamoDB Accelerator (DAX) to cache writes

Answer

Increase the provisioned write capacity units (WCU) to a higher value

Answer

Change the table design to use only partition key 'user_id' and remove the sort key

Question 4

A SysOps administrator is tasked with monitoring the free storage space on all Amazon RDS DB instances. Which AWS service should be used to set up an alarm that sends an email notification when free storage space falls below a threshold?

Accepted Answer

Amazon CloudWatch with an alarm on the FreeStorageSpace metric and an SNS topic.. Amazon CloudWatch provides the `FreeStorageSpace` metric for RDS DB instances, which reports the amount of available storage in bytes. You can create a CloudWatch alarm on this metric and configure it to send a notification via an Amazon SNS topic when the value falls below a specified threshold, enabling proactive monitoring of storage capacity.

Answer

AWS CloudTrail to monitor storage events.

Answer

AWS Config to track storage configuration changes.

Answer

Amazon Inspector to check for storage vulnerabilities.

Question 5

A company uses Amazon DynamoDB with fine-grained access control based on user identity. The IAM policy for a user includes a condition that restricts access to items where the 'department' attribute equals 'engineering'. However, the user is receiving an 'AccessDeniedException' when trying to query items. What is the most likely cause?

Accepted Answer

The 'department' attribute is not the partition key of the table.. Fine-grained access control in DynamoDB uses IAM policy conditions with the 'dynamodb:LeadingKeys' or 'dynamodb:Attributes' condition keys. The 'department' attribute must be the partition key of the table for 'LeadingKeys' to work. If 'department' is not the partition key, the condition cannot be evaluated for the query. Option A is possible but less likely if the user is using the correct role. Option C is wrong because DynamoDB does not require SSL for all operations. Option D is wrong because Condition check is exactly how it works.

Answer

The user is not using the correct IAM role.

Answer

The DynamoDB table is not configured to require SSL.

Answer

The IAM policy is missing a 'Condition' block.

Question 6

A company is migrating a 500 GB PostgreSQL database from on-premises to Amazon Aurora PostgreSQL. They need to minimize downtime and ensure that all data changes made during migration are synchronized. Which three components are required for this migration? (Choose THREE.)

Accepted Answer

AWS Database Migration Service (DMS) replication instance. AWS DMS replication instance is required because it orchestrates the continuous replication of data from the source PostgreSQL database to the target Aurora PostgreSQL cluster. It manages the connection, reads changes from the source using logical replication slots, and applies them to the target, enabling near-zero downtime migration.

Answer

AWS Schema Conversion Tool (SCT)

Answer

AWS VPN connection between on-premises and AWS

Question 7

A company runs an OLTP workload on an RDS for MySQL instance. The database has a table with 50 million rows. The application frequently runs queries that join this table with a small lookup table (1000 rows) using a foreign key. The queries are slow. Which design change would most improve performance?

Accepted Answer

Add an index on the foreign key column in the large table.. The query joins a large table (50M rows) with a small lookup table (1000 rows) on a foreign key column. Without an index on the foreign key column in the large table, MySQL must perform a full table scan for each join, leading to slow performance. Adding an index on that column allows MySQL to use an index lookup (e.g., B-tree) to quickly locate matching rows, dramatically reducing query time.

Answer

Partition the large table by the foreign key column.

Answer

Scale up the RDS instance to a larger size.

Answer

Create a read replica and direct all read queries to it.

Question 8

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database contains sensitive data that must be encrypted at rest. Which action should the company take to enable encryption on the RDS instance?

Accepted Answer

Create a new RDS DB instance with encryption enabled and migrate the data.. Amazon RDS for Oracle supports encryption at rest using AWS KMS. Encryption can only be enabled when the DB instance is created; you cannot encrypt an existing unencrypted RDS instance. Therefore, to enable encryption for an existing on-premises Oracle database being migrated, you must create a new RDS DB instance with encryption enabled at launch and then migrate the data into that new instance. This makes option B the correct choice. Option A is incorrect because you cannot modify an existing unencrypted RDS instance to add encryption. Option C is incorrect because while Oracle Transparent Data Encryption (TDE) can be used to encrypt data within the database, it is not the native Amazon RDS encryption method and requires additional configuration; moreover, the scenario assumes a new RDS instance is being created, not an existing one. Option D is incorrect because the source database is on-premises, not an RDS instance, so there is no RDS snapshot to take; even if there were an existing unencrypted RDS instance, encrypting a snapshot requires copying it with encryption enabled, not directly encrypting the snapshot. Thus D is not a valid action for this migration.

Answer

Modify the existing RDS DB instance and enable encryption.

Answer

Enable Oracle Transparent Data Encryption (TDE) on the existing RDS instance.

Answer

Take a snapshot of the existing database, encrypt the snapshot, and restore from it.

Question 9

A financial services company runs an Amazon Aurora MySQL database. The application performs complex joins and aggregations on large tables, causing high CPU utilization on the writer instance. The team wants to reduce load without changing the application code. Which solution would best address this issue?

Accepted Answer

Create one or more Aurora Replicas and route read traffic to them.. Creating one or more Aurora Replicas and routing read traffic to them offloads the complex joins and aggregations from the writer instance, reducing CPU utilization without requiring application code changes. Aurora Replicas share the same underlying storage volume as the writer, so they serve read queries with minimal replication lag while the writer focuses on write operations.

Answer

Switch to asynchronous replication to reduce load on the primary.

Answer

Enable Aurora Auto Scaling to increase storage capacity.

Answer

Migrate to Aurora Serverless v2 for automatic scaling.

Question 10

A company is running a production Amazon RDS for MySQL Multi-AZ DB instance. The database administrator needs to perform a minor version upgrade with minimal downtime. Which TWO actions should be taken? (Choose TWO.)

Accepted Answer

Modify the DB instance to enable automatic minor version upgrade.. Enabling automatic minor version upgrades on an RDS for MySQL Multi-AZ instance allows Amazon RDS to apply the upgrade during the next maintenance window with minimal downtime. During the upgrade, RDS patches the standby first, then performs a failover to make the standby the new primary, resulting in a brief (typically under 60 seconds) interruption rather than a full outage. This approach leverages the Multi-AZ architecture to reduce downtime compared to manual upgrades.

Answer

Create a read replica, upgrade the replica, and promote it.

Answer

Modify the DB instance to be a Single-AZ deployment to simplify the upgrade.

Answer

Stop the DB instance before applying the upgrade.