DBS-C01 Practice Test 46 — 15 Questions

Question 1

A database specialist needs to enforce that all data stored in an Amazon RDS for MySQL DB instance is encrypted at rest using a customer managed AWS KMS key rather than the default AWS managed key. The instance was created without encryption. Which action should the database specialist take?

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

Accepted Answer

Take a snapshot, copy it with encryption enabled using the customer managed KMS key, and restore a new instance from the encrypted snapshot.. RDS encryption at rest is set at instance creation and cannot be toggled on an existing instance. The supported conversion path is to snapshot the unencrypted instance, copy that snapshot while enabling encryption with the chosen customer managed KMS key, then restore a new instance from the encrypted snapshot. This yields storage encrypted under the specified key.

Answer

Enable encryption by modifying the underlying DB parameter group to require TLS for all connections.

Answer

Create an encrypted read replica using the customer managed KMS key, then promote it to a standalone instance.

Answer

Modify the DB instance and enable encryption, specifying the customer managed KMS key.

Question 2

A company has an Amazon DynamoDB table with on-demand capacity mode. They notice that write requests are being throttled during peak hours. The table has a global secondary index (GSI) that is also throttled. Which action should the database specialist take to resolve the throttling?

Accepted Answer

Review the partition key design and consider adding a suffix to distribute writes more evenly.. The throttling of both the base table and the GSI during peak hours indicates a hot partition caused by an uneven distribution of write activity. Reviewing the partition key design and adding a suffix to distribute writes more evenly is the correct action because it addresses the root cause: DynamoDB's on-demand mode automatically scales capacity, but it cannot overcome a skewed access pattern that overloads a single partition. By spreading writes across more partitions, you eliminate the hot spot and prevent throttling without changing capacity mode.

Answer

Enable DynamoDB Streams to offload write operations.

Answer

Switch to provisioned capacity mode and increase write capacity units (WCU).

Answer

Increase the write capacity of the GSI by updating the table's provisioned throughput.

Question 3

A company is designing a database for a social media application that requires low-latency access to user profiles and support for complex graph queries. Which AWS database service is most suitable for this workload?

Accepted Answer

Amazon Neptune. Amazon Neptune 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 the ideal choice for social media applications that require low-latency traversal of complex relationships, such as friend-of-friend recommendations or influence paths.

Answer

Amazon DynamoDB

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Amazon ElastiCache for Redis

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Amazon RDS for MySQL

Question 4

A company is deploying Amazon RDS for PostgreSQL and needs to ensure that all data at rest is encrypted. Which action should be taken to enable encryption?

Accepted Answer

Specify an AWS KMS key when creating the RDS instance.. Amazon RDS for PostgreSQL supports encryption at rest using AWS Key Management Service (KMS). Encryption must be enabled at instance creation time by specifying an AWS KMS key; it cannot be enabled on an existing unencrypted instance. This ensures that the underlying storage, automated backups, read replicas, and snapshots are encrypted using the chosen KMS key.

Answer

Modify the existing RDS instance to enable encryption.

Answer

Enable encryption by default in the RDS console.

Answer

Enable encryption using S3 server-side encryption.

Question 5

Which TWO metrics should be monitored to detect a memory leak in an RDS for Oracle instance? (Choose 2.)

Accepted Answer

SwapUsage. SwapUsage (A) is correct because a memory leak in RDS for Oracle causes the instance to exhaust physical RAM and begin paging to the swap file, so rising SwapUsage is a direct indicator of memory pressure from a leak. FreeableMemory (B) is correct because it reports the amount of available RAM on the DB instance; a steadily declining FreeableMemory trend over time, without a corresponding workload increase, is the classic signature of a memory leak. DatabaseConnections (C) is not correct because it only counts active sessions and does not measure memory consumption. CPUUtilization (D) is not correct because high CPU can stem from many causes and does not specifically indicate leaked memory. ReadIOPS (E) is not correct because it measures read I/O operations, which may rise with swapping but is not a direct memory-leak metric.

Answer

DatabaseConnections

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CPUUtilization

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ReadIOPS

Question 6

A company is using Amazon ElastiCache for Redis to cache frequently accessed data. Recently, the application has been experiencing increased latency. The database specialist suspects that the cache hit ratio has decreased. Which CloudWatch metric should the specialist analyze to confirm this suspicion?

Accepted Answer

Monitor 'CacheHits' and 'CacheMisses' metrics to calculate the hit ratio.. The cache hit ratio is calculated as CacheHits / (CacheHits + CacheMisses). Monitoring the 'CacheHits' and 'CacheMisses' CloudWatch metrics allows the specialist to compute the hit ratio and confirm whether it has decreased, which would explain increased latency. Option A is incorrect because CurrConnections shows the number of connections, not the cache hit ratio. Option B is incorrect because Evictions indicates keys being evicted, which can affect the cache but does not directly measure the hit ratio. Option D is incorrect because ReplicationLag measures replication delay, not cache performance.

Answer

Monitor the 'CurrConnections' metric to see if there are too many connections.

Answer

Monitor the 'Evictions' metric to see if keys are being evicted.

Answer

Monitor the 'ReplicationLag' metric to check replication delay.

Question 7

A company wants to deploy an Amazon RDS for MySQL database for a new application. The database must be highly available with automatic failover. Which configuration should they choose?

Accepted Answer

Deploy a Multi-AZ instance with a standby replica. A Multi-AZ deployment for Amazon RDS automatically provisions and maintains a synchronous standby replica in a different Availability Zone. In the event of a failure, Amazon RDS automatically fails over to the standby, providing high availability without manual intervention. This configuration meets the requirement for automatic failover and high availability.

Answer

Deploy a single-AZ instance with automated backups

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Deploy a cross-region replica

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Deploy a single-AZ instance with a read replica

Question 8

Which TWO factors should be considered when selecting a migration method from on-premises Oracle to Amazon RDS for Oracle?

Accepted Answer

The size of the database and available network bandwidth. Option A is correct because the database size combined with available network bandwidth directly determines how long a network-based migration (for example, Oracle Data Pump over a VPN or AWS Direct Connect, or AWS DMS) will take, which drives the choice between methods such as Data Pump, DMS, or physical/logical approaches. Option C is correct because the acceptable downtime window dictates whether you can use a simple offline export/import or need a minimal-downtime approach like AWS DMS with ongoing replication or Oracle Data Guard/Active Data Guard. Option B is not a primary selection factor because the Oracle client version affects application connectivity compatibility, not the migration method itself. Option D is not a primary factor because stored procedure count does not determine the migration mechanism, though it may influence post-migration validation effort. Option E is not a primary factor because the number of indexes affects migration performance and post-load index rebuild time, but not the fundamental choice of migration method.

Answer

The version of the Oracle client used by applications

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The number of stored procedures in the database

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The number of indexes on the source database

Question 9

A company is using Amazon ElastiCache for Redis and notices that the cache hit ratio is low. The application is frequently reading data that is not in the cache. Which action would be most effective in improving the cache hit ratio?

Accepted Answer

Pre-warm the cache by loading frequently accessed data from the database.. A low cache hit ratio means that many requests are missing the cache and going to the database. Pre-warming the cache by loading frequently accessed data ensures that the data most likely to be requested is already in the cache, directly increasing the hit ratio. This is a proactive approach to populate the cache with relevant data.

Answer

Increase the number of replicas in the replication group.

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Decrease the TTL of cached items to ensure freshness.

Answer

Enable Multi-AZ for automatic failover.

Question 10

A company is using Amazon Aurora MySQL-Compatible Edition. The database administrator wants to restrict a specific user to only execute SELECT statements on a specific database. Which SQL command should the administrator use?

Accepted Answer

GRANT SELECT ON db_name.* TO 'user'@'%';. The GRANT statement is the standard SQL command to assign privileges to a user. GRANT SELECT ON db_name.* TO 'user'@'%' grants only SELECT privileges on all tables in the specified database, which exactly matches the requirement to restrict the user to SELECT statements on a specific database. This is the least-privilege approach.

Answer

ALTER USER 'user'@'%' WITH GRANT OPTION;

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CREATE USER 'user'@'%' IDENTIFIED BY 'password';

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REVOKE ALL PRIVILEGES ON db_name.* FROM 'user'@'%';

Question 11

A company runs a PostgreSQL database on an Amazon RDS DB instance (db.t3.medium) with 100 GB of General Purpose SSD (gp2) storage. The database is used by a web application that experiences occasional slowdowns. CloudWatch metrics show that the BurstBalance metric for the storage volume drops to 0% during peak usage and then recovers. The average IOPS during peak is 600, and the baseline IOPS for the volume is 300. The team needs a cost-effective solution to eliminate the performance issues. What should the team do?

Accepted Answer

Migrate the storage to gp3 with 3000 baseline IOPS.. The gp2 volume's BurstBalance dropping to 0% indicates the burst bucket is exhausted, and the baseline IOPS for a 100 GB gp2 volume is only 300 IOPS (3 IOPS/GB). Peak demand of 600 IOPS exceeds baseline, so performance degrades once credits run out. Migrating to gp3 provides a flat 3000 baseline IOPS regardless of volume size, eliminating the burst-credit dependency at a lower cost than over-provisioning gp2.

Answer

Upgrade the DB instance to db.t3.large.

Answer

Increase the gp2 volume size to 200 GB.

Answer

Enable Performance Insights to monitor database load.

Question 12

A company uses Amazon Aurora MySQL for its customer relationship management (CRM) system. The database has a table "contacts" with millions of rows. The application frequently searches for contacts by email address. The email column has a B-tree index. The DBA notices that queries are still slow, and the EXPLAIN plan shows index scans but not index-only scans. What is the most likely cause?

Accepted Answer

The query selects columns not included in the index, requiring table lookups.. An index-only scan requires that all columns referenced in the query (both in the SELECT list and WHERE clause) be present in the index. Since the query selects columns not included in the B-tree index on the email column, Aurora MySQL must perform additional table lookups (row fetches) to retrieve those missing columns, resulting in an index scan rather than an index-only scan.

Answer

The index is a composite index on (email, phone) and the query selects only email.

Answer

The index has low cardinality.

Answer

The index type is not suitable for equality searches.

Question 13

A database administrator notices that an Amazon RDS for SQL Server DB instance has been in the 'storage-optimization' state for several hours after modifying the storage type from gp2 to io1. What should the administrator do to resolve this?

Accepted Answer

Wait for the storage optimization to complete.. The 'storage-optimization' state indicates that RDS is performing a background storage modification, such as changing storage type or increasing allocated storage. This is a normal, expected state and the administrator should simply wait for it to complete. The modification is applied asynchronously, and the DB instance remains available during the process, though performance may be slightly impacted. Attempting to cancel or reboot will not speed up the process and could cause issues.

Answer

Restore from the latest snapshot and reapply the modification.

Answer

Cancel the modification by modifying the DB instance back to gp2.

Answer

Reboot the DB instance.

Question 14

A company is migrating an on-premises MongoDB database to Amazon DocumentDB. The migration must be online with minimal downtime. The source MongoDB is version 4.0 and uses replica sets. Which tool should the company use?

Accepted Answer

Use AWS DMS with MongoDB as source and DocumentDB as target.. AWS DMS (Database Migration Service) supports continuous replication from MongoDB (including replica sets) to Amazon DocumentDB, enabling an online migration with minimal downtime. DMS uses the MongoDB oplog to capture ongoing changes, ensuring data consistency during the cutover. This is the only option that meets the requirement for an online migration with minimal downtime.

Answer

Use MongoDB Compass to export data and import into DocumentDB.

Answer

Use mongodump and mongorestore.

Answer

Create a read replica of the MongoDB replica set and promote to DocumentDB.

Question 15

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