DBS-C01 Practice Test 33 — 15 Questions

Question 1

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.

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Amazon DocumentDB

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Amazon ElastiCache

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Amazon DynamoDB

Question 2

Which TWO of the following are valid considerations when designing a database for an e-commerce application with high read traffic and low write latency requirements?

Accepted Answer

Use Amazon DynamoDB Accelerator (DAX) to improve read performance.. Option A is correct because Amazon DynamoDB Accelerator (DAX) is an in-memory cache purpose-built for DynamoDB that delivers microsecond read latency for read-heavy workloads, directly addressing the high read traffic requirement. Option D is correct because Amazon ElastiCache (Redis or Memcached) caches frequently accessed data in memory, offloading read pressure from the primary database and reducing latency for hot items such as product catalogs. Option B is wrong because Amazon S3 is object storage with relatively high latency and eventual consistency characteristics, making it unsuitable for fast session access compared to ElastiCache or DynamoDB. Option C is wrong because Amazon Redshift is a columnar data warehouse optimized for analytical (OLAP) queries, not for serving high-volume transactional read traffic. Option E is wrong because RDS Multi-AZ provides high availability through a standby replica that does not serve read traffic; read scaling requires read replicas, not Multi-AZ.

Answer

Store session data in Amazon S3 for fast access.

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Use Amazon Redshift to serve read traffic directly.

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Deploy Amazon RDS for MySQL with Multi-AZ for read scaling.

Question 3

A company uses Amazon DynamoDB with global tables for a multi-region application. The application writes to the table in us-east-1. A developer notices that updates made in us-east-1 are not appearing in the replica in eu-west-1 after several minutes. Which action should be taken to diagnose the issue?

Accepted Answer

Review the CloudWatch metrics for ReplicationLatency and PendingReplicationCount for the global table.. For DynamoDB global tables, replication health is monitored through CloudWatch metrics specific to the global table: ReplicationLatency (the time between when a write occurs in one region and when it is applied in another) and PendingReplicationCount (the number of item updates waiting to be replicated). These metrics directly indicate whether replication is lagging or stuck, making them the correct first diagnostic step. Reviewing them will show if the delay is due to normal latency, throttling, or a configuration issue.

Answer

Modify the application to use the eu-west-1 endpoint for writes.

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Check that the table has an active DynamoDB Streams stream with StreamSpecification set to KEYS_ONLY.

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Verify that the TTL attribute on the table is correctly configured.

Question 4

A team is using Amazon RDS for Oracle with an option group that includes the Oracle Enterprise Manager (OEM) option. After modifying the option group to add a new option, the DB instance is stuck in the 'modifying' state for an extended period. What should the team do?

Accepted Answer

Reboot the DB instance to complete the modification.. When an option group modification requires a reboot, the DB instance remains in the 'modifying' state until the reboot is applied. For RDS for Oracle, adding certain options like OEM requires a reboot to take effect, so the team should reboot the DB instance to complete the modification. This is documented AWS behavior for options that have the 'requires reboot' attribute.

Answer

Contact AWS Support to force the modification.

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Create a new DB instance with the desired options and migrate the data.

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Modify the DB instance again to reset the state.

Question 5

Refer to the exhibit. An IAM policy is attached to a user. The user reports that they cannot delete the production-db database. Which statement best explains the behavior?

Accepted Answer

An explicit Deny statement prevents the deletion of the production-db instance. The IAM policy attached to the user contains an explicit Deny statement for the rds:DeleteDBInstance action on the production-db resource. In AWS IAM, an explicit Deny always overrides any Allow, regardless of the permissions granted elsewhere. Therefore, even if the user has other policies that allow deletion, the explicit Deny in this policy blocks the action, resulting in the observed behavior.

Answer

The user needs additional permissions to delete any DB instance

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The user does not have permission to describe DB instances

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The user does not have permission to create a DB instance

Question 6

A database specialist is troubleshooting a performance issue on an Amazon RDS for MySQL DB instance. The CPU utilization is consistently above 90%, but the IOPS and memory metrics are well within limits. Which tool should the specialist use to identify the root cause?

Accepted Answer

Use Amazon RDS Performance Insights to identify the top SQL queries by CPU usage.. Amazon RDS Performance Insights provides a database performance tuning and monitoring feature that visualizes database load and helps identify the top SQL queries consuming the most CPU. Since the CPU is consistently above 90% while IOPS and memory are normal, Performance Insights can directly correlate high CPU usage to specific SQL statements, enabling the specialist to pinpoint the root cause efficiently.

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Enable AWS CloudTrail to log database queries.

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Use Amazon RDS Enhanced Monitoring to view OS-level metrics.

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Check RDS events in the AWS Management Console.

Question 7

A company uses Amazon Redshift for data warehousing. The security team requires that all data be encrypted at rest with a customer-managed key, and that the key be rotated every year. Which configuration meets these requirements?

Accepted Answer

Launch the Redshift cluster with encryption enabled using a customer-managed KMS key with automatic annual rotation.. Amazon Redshift supports encryption at rest using AWS KMS customer-managed keys, and KMS customer-managed keys support automatic annual rotation. This combination satisfies both the customer-managed key requirement and the yearly rotation requirement without manual intervention.

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Launch the Redshift cluster without encryption and enable encryption later using AWS CloudHSM.

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Launch the Redshift cluster with encryption enabled using an S3-managed key.

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Launch the Redshift cluster with encryption enabled using a KMS key and configure the cluster to use an HSM for key storage.

Question 8

A company is using Amazon RDS for MySQL with a cross-Region read replica to support disaster recovery. The primary DB instance is in us-west-2, and the read replica is in us-east-1. The read replica is used for reporting and also serves as a failover target. The operations team notices that the read replica lag is consistently above 10 seconds during peak hours. What should the team do to reduce replica lag?

Accepted Answer

Increase the DB instance class of the read replica.. Increasing the DB instance class of the read replica provides more CPU and memory resources, which allows the replica to apply changes from the binary log more quickly. Cross-Region replication lag is often caused by the replica being unable to keep up with the write rate on the primary, so scaling up the replica directly addresses the bottleneck in applying binlog events.

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Enable Multi-AZ on the primary DB instance.

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Increase the backup retention period for the primary DB instance.

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Disable binary logging (binlog) on the primary DB instance.

Question 9

Match each RDS storage type to its description.

Accepted Answer

General Purpose SSD: Balanced price and performance, suitable for most database workloads.. Correct matches: General Purpose SSD balances price and performance; Provisioned IOPS SSD provides high, consistent performance; Magnetic is low-cost for infrequent access. Common confusions include swapping the descriptions of General Purpose and Provisioned IOPS, or associating low cost with Provisioned IOPS.

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General Purpose SSD: High performance with consistent low latency.

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Magnetic: Balanced price and performance.

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Provisioned IOPS SSD: Lowest cost, suitable for infrequently accessed data.

Question 10

A small business runs a web application on a single Amazon RDS for MySQL DB instance. The application uses a master user account for all database operations. The security team is concerned about the risk of SQL injection and wants to implement the principle of least privilege. They want to create separate database users for read-only and read-write operations. The application currently uses a single connection string. The developer needs to modify the application to use two separate users. What is the correct approach to implement this securely?

Accepted Answer

Create a read-only user and a read-write user in the database, grant minimal privileges, and modify the application to use the appropriate user for each operation.. Creating separate users with minimal privileges and modifying the application to use the appropriate user for each operation reduces the risk of SQL injection and enforces least privilege. Option A is wrong because using stored procedures with a single master user does not eliminate the need for separate users for different privilege levels. Option B is wrong because restricting IP address does not address the need for granular permissions. Option C is wrong because enabling IAM database authentication with a single IAM role does not provide separate read-only and read-write capabilities.

Answer

Use stored procedures for all database operations and grant execute only to the master user.

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Keep using the master user but restrict its IP address.

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Enable IAM database authentication and use a single IAM role.

Question 11

A financial services company is migrating a 2 TB Oracle database to Amazon Aurora PostgreSQL. The database uses Oracle-specific features like hierarchical queries and stored procedures. The company wants to minimize manual code changes. Which service should be used to automate schema conversion?

Accepted Answer

AWS Schema Conversion Tool (SCT).. AWS Schema Conversion Tool (SCT) is specifically designed to convert database schemas from one engine to another, including Oracle to Amazon Aurora PostgreSQL. It automates the conversion of Oracle-specific features like hierarchical queries (CONNECT BY) and stored procedures into PostgreSQL-compatible syntax (e.g., recursive CTEs and PL/pgSQL), minimizing manual code changes. This makes SCT the correct choice for schema conversion, while AWS DMS handles data migration separately.

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AWS Database Migration Service (DMS) with full load and ongoing replication.

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AWS Storage Gateway to cache data on-premises and then sync to S3.

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AWS Lambda to execute custom scripts for schema transformation.

Question 12

A developer executed a DELETE statement without a WHERE clause on an Amazon RDS for PostgreSQL instance. The transaction is still open. Which action should the developer take to undo the DELETE without affecting other operations?

Accepted Answer

Execute ROLLBACK in the same session.. The correct action is to execute ROLLBACK in the same session. Since the transaction is still open, issuing ROLLBACK will undo the DELETE statement without affecting other operations. Option A is incorrect because COMMIT would make the DELETE permanent. Option B is incorrect because Point-in-Time Recovery restores the entire DB instance to a past state, which is unnecessary and affects other data. Option D is incorrect because stopping and restoring from a snapshot would also affect other data and is not the simplest solution.

Answer

Execute COMMIT and then run a recovery script.

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Use the Point-in-Time Recovery feature to restore the database to a time before the DELETE.

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Stop the DB instance and restore from the latest snapshot.

Question 13

A company is using Amazon DynamoDB for a gaming leaderboard that updates frequently. They need to maintain a sorted list of top 100 players by score. Which THREE design patterns can achieve this efficiently?

Accepted Answer

Use a Global Secondary Index (GSI) with score as the sort key and query with ScanIndexForward=false and Limit=100.. A Global Secondary Index (GSI) with score as the sort key allows you to query items in descending order using ScanIndexForward=false and limit the result to the top 100 players. This pattern efficiently retrieves the highest scores without scanning the entire table, leveraging DynamoDB's index query capabilities.

Answer

Use DynamoDB Accelerator (DAX) to cache query results.

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Scan the entire table and sort the results in memory.

Question 14

A company is designing a database for a real-time leaderboard in a mobile game. The leaderboard updates thousands of times per second and must return the top 100 scores with minimal latency. Which AWS database service is most suitable for this workload?

Accepted Answer

Amazon ElastiCache for Redis. Amazon ElastiCache for Redis is the most suitable choice because Redis provides an in-memory data structure server with a Sorted Set data type (ZADD and ZRANGE commands) that natively supports real-time leaderboard operations. It can handle thousands of writes per second with sub-millisecond latency and efficiently retrieve the top 100 scores using ZREVRANGE with a time complexity of O(log(N)+M), where M is the number of returned elements.

Answer

Amazon Neptune

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Amazon DynamoDB

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Amazon Aurora

Question 15

A company needs to encrypt an existing unencrypted Amazon RDS for Oracle DB instance. Which set of steps should be followed?

Accepted Answer

Take a snapshot of the instance, copy the snapshot with encryption enabled, and restore from the encrypted snapshot.. To encrypt an existing unencrypted RDS for Oracle DB instance, you must take a snapshot, copy the snapshot with encryption enabled, and then restore from the encrypted snapshot. This creates a new encrypted DB instance. Encryption cannot be enabled directly on an existing unencrypted instance.

Answer

Enable encryption using the AWS Management Console by selecting the instance and choosing 'Enable Encryption'.

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Modify the DB instance and set the KMS key ID to enable encryption.

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Copy the snapshot to an encrypted snapshot and then restore.