DBS-C01 Practice Test 6 — 10 Questions

Question 1

A startup is building a social media analytics platform that requires storing time-series data with frequent writes and queries for the last hour. Which AWS database service is BEST suited for this workload?

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

Accepted Answer

Amazon Timestream. Amazon Timestream is a purpose-built time-series database that efficiently handles high-frequency writes and recent-time queries (e.g., last hour) with automatic data tiering (in-memory store for recent data, magnetic store for historical). Its serverless architecture and built-in time-series functions (e.g., interpolation, smoothing) make it ideal for social media analytics workloads requiring low-latency queries on recent data.

Answer

Amazon RDS with MySQL

Answer

Amazon Neptune

Answer

Amazon DynamoDB

Question 2

A company is running an Amazon RDS for PostgreSQL DB instance with Multi-AZ deployment. They notice that the primary DB instance is experiencing high CPU utilization. The read replica shows normal CPU. Which action should the DBA take to reduce the load on the primary instance?

Accepted Answer

Offload SELECT queries to the read replica. Offloading SELECT queries to the read replica reduces CPU utilization on the primary instance because read replicas can handle read traffic independently. Option A is incorrect: failing over to the standby instance does not reduce CPU load—the standby is only for high availability and becomes the new primary, still handling the same workload. Option B is incorrect: increasing the DB instance size would help but is not the best first step; it involves scaling costs and potential downtime, whereas using a read replica is more efficient and cost-effective for read-heavy workloads. Option C is incorrect: converting the read replica to a Multi-AZ standby would make it a synchronous replica for failover, not for offloading reads, so it would not reduce CPU on the primary.

Answer

Failover to the standby instance

Answer

Increase the DB instance size

Answer

Convert the read replica to a Multi-AZ standby

Question 3

A company is migrating an on-premises MySQL database to Amazon RDS for MySQL. They need to validate that the schema is compatible. Which AWS service should they use?

Accepted Answer

AWS Schema Conversion Tool (SCT). The AWS Schema Conversion Tool (SCT) is designed specifically to assess and convert database schemas from one engine to another, including on-premises MySQL to Amazon RDS for MySQL. It analyzes the source schema for compatibility issues, identifies unsupported features or deprecated syntax, and generates a detailed assessment report. This makes it the correct choice for validating schema compatibility before migration.

Answer

Amazon Inspector

Answer

AWS Database Migration Service (DMS)

Answer

AWS Trusted Advisor

Question 4

A company is using Amazon ElastiCache for Redis to cache database query results. The application team reports that cache hit ratio has dropped significantly. What is the first step to investigate?

Accepted Answer

Check the CacheHitRate and Evictions metrics in CloudWatch. When the cache hit ratio drops significantly, the first step is to investigate whether the cache is evicting keys due to memory pressure or if the working set no longer fits. CloudWatch metrics such as `CacheHitRate` and `Evictions` provide immediate visibility into these conditions without requiring direct Redis access. This aligns with the AWS Well-Architected Framework's principle of observability before making configuration changes.

Answer

Run the Redis INFO command to see memory usage

Answer

Review the ElastiCache event logs for node failures

Answer

Check the Redis AOF persistence logs

Question 5

A company wants to audit all SQL statements executed on their Amazon Aurora MySQL database for compliance. Which AWS feature should be enabled?

Accepted Answer

Database Activity Streams. Database Activity Streams provide a stream of database activities including SQL queries. Option B is wrong because VPC Flow Logs capture network traffic, not SQL statements. Option C is wrong because CloudWatch Logs can store logs but the source should be Database Activity Streams; CloudWatch Logs alone does not audit SQL statements. Option D is wrong because CloudTrail logs API calls, not SQL statements.

Answer

VPC Flow Logs

Answer

Amazon CloudWatch Logs

Answer

AWS CloudTrail

Question 6

A security engineer is investigating an Amazon RDS for MySQL database that was compromised. The engineer finds that the compromise was due to a SQL injection vulnerability in a web application. The web application uses a database user with full administrative privileges. What is the BEST practice to prevent such incidents in the future?

Accepted Answer

Create dedicated database users with minimal privileges required for each application function.. The best practice is to use dedicated database users with minimal privileges for each application function (Option A). This principle of least privilege limits the damage a SQL injection attack can cause because the compromised user cannot perform unauthorized actions beyond its specific scope. Option B is incorrect because the 'sql_mode' parameter can reject certain dangerous queries but does not address the root cause of excessive privileges and may not prevent all injection attacks. Option C is incorrect because audit logs only help detect incidents after they occur, not prevent them. Option D is incorrect because while placing the RDS instance in a private subnet and restricting inbound traffic reduces the network attack surface, it does not prevent SQL injection attacks that originate from the application itself; the vulnerability lies in how the application interacts with the database.

Answer

Configure the DB parameter group to use the 'sql_mode' option to reject dangerous queries.

Answer

Enable RDS audit logs to capture all SQL queries.

Answer

Place the RDS instance in a private subnet with a security group that restricts inbound traffic.

Question 7

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 8

A company wants to migrate an on-premises MySQL database to Amazon RDS for MySQL with minimal downtime. They plan to use AWS DMS. Which source database configuration is required to enable ongoing replication (CDC)?

Accepted Answer

Enable binary logging (binlog) on the source database. AWS DMS requires binary logging (binlog) enabled on the source MySQL database to capture ongoing changes for continuous replication (CDC). The binlog records all data modifications (INSERT, UPDATE, DELETE) in a sequential log, which DMS reads to apply those changes to the target RDS instance with minimal downtime. Without binlog enabled, DMS can only perform a full load migration and cannot support ongoing replication.

Answer

Set auto_increment_increment to 1

Answer

Enable the slow query log

Answer

Enable the query cache

Question 9

A company uses Amazon Aurora MySQL-Compatible Edition. The security team wants to implement database activity streams to monitor database activity. Which THREE statements are true about Aurora database activity streams?

Accepted Answer

Activity streams can be started and stopped without restarting the database.. Options A, B, and E are correct. Activity streams can be started and stopped without a database restart (A). They are encrypted using a KMS key (B). They publish database activity to Amazon CloudWatch Logs and Amazon Kinesis Firehose (E). Option C is incorrect because activity streams do not automatically mask sensitive data; they capture the actual queries. Option D is incorrect because activity streams capture all SQL statements, including DDL, DML, and SELECT.

Answer

Activity streams automatically mask sensitive data in the logs.

Answer

Activity streams only capture DDL statements, not DML or SELECT.

Question 10

A company is running an Amazon RDS for MySQL DB instance in a VPC. The security team requires that all connections to the database use SSL/TLS. The DBA has enabled 'require_secure_transport' parameter in the DB parameter group. However, after applying the change and rebooting, some applications that were previously connecting successfully are now failing. What is the most likely cause?

Accepted Answer

The application is not configured to connect using SSL/TLS.. The most likely cause is that the application is not configured to connect using SSL/TLS. When 'require_secure_transport' is enabled, the database rejects any non-SSL connections. Applications that were previously connecting without SSL will fail until they are updated to use SSL/TLS in their connection strings. The parameter change itself is correct and does not require an option group modification for RDS MySQL.

Answer

The security group inbound rule for the database port is missing.

Answer

The option group does not have the SSL option enabled.

Answer

The DB subnet group does not include the application's subnet.