DBS-C01 Practice Test 18 — 15 Questions

Question 1

A company is running an Amazon RDS for MySQL database. The application team reports that the database is slow. Upon investigation, you notice that the DB instance's CPU utilization is consistently above 90%. Which initial troubleshooting step should you take?

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

Accepted Answer

Enable Enhanced Monitoring to identify the source of high CPU usage.. When CPU utilization is consistently above 90% on an RDS for MySQL instance, the correct first step is to gather diagnostic data rather than blindly scaling. Enhanced Monitoring provides OS-level metrics (per-process CPU, memory, disk I/O) at up to 1-second granularity, which lets you pinpoint whether the CPU is consumed by the MySQL process, a specific query, or an external agent. Only after identifying the root cause can you choose the right remediation, such as query tuning, indexing, or a vertical scale.

Answer

Increase the DB instance size to improve performance.

Answer

Delete the slow query logs to reduce I/O.

Answer

Change the storage type from General Purpose (gp2) to Provisioned IOPS (io1).

Question 2

A logistics company uses Amazon RDS for MySQL to track package shipments. The 'shipments' table contains 200 million rows and has a primary key on 'shipment_id' (UUID). The application frequently queries for shipments by 'tracking_number', which is a unique string of 20 characters. The DBA created a B-tree index on tracking_number. The queries by tracking_number are fast, but inserts are becoming slower over time. The table has 50 GB of data. The company plans to double the insert rate next month. The database is a db.r5.large instance with 500 GB of Provisioned IOPS SSD storage. The instance's CPU utilization is below 30%, and there is no lock contention. What should the database specialist do to improve insert performance?

Accepted Answer

Change the primary key from UUID to an auto-increment integer, and keep the tracking_number index.. UUID primary keys cause random writes and index fragmentation, degrading insert performance as the table grows. Switching to an auto-increment integer primary key allows sequential writes to the clustered index, reducing page splits and improving insert throughput. The B-tree index on tracking_number remains to support fast queries, while the new primary key eliminates the UUID write overhead.

Answer

Add a read replica and route insert queries to the replica.

Answer

Drop the index on tracking_number to reduce write overhead.

Answer

Increase the provisioned IOPS to 20,000.

Question 3

Which TWO of the following are valid methods to migrate an on-premises MySQL database to Amazon RDS for MySQL? (Select TWO.)

Accepted Answer

Use AWS DMS to migrate from on-premises MySQL to RDS.. Option B is correct because AWS Database Migration Service (DMS) natively supports MySQL as both a source and a target endpoint, allowing both one-time and ongoing (CDC) replication from on-premises MySQL into Amazon RDS for MySQL. Option E is correct because mysqldump is the standard MySQL-native logical backup utility; it produces SQL statements that can be piped or loaded directly into an RDS for MySQL instance, making it a valid migration method. Option A is incorrect because pg_dump is a PostgreSQL utility and cannot export MySQL data. Option C is incorrect because SQL Server Integration Services (SSIS) is a Microsoft SQL Server ETL tool, not a MySQL migration mechanism. Option D is incorrect because Oracle Data Pump (expdp/impdp) works only with Oracle databases and is incompatible with MySQL.

Answer

Use pg_dump to export the data and import into RDS.

Answer

Use SQL Server Integration Services (SSIS) to migrate the data.

Answer

Use Oracle Data Pump to export the data and import into RDS.

Question 4

Refer to the exhibit. An IAM policy is attached to an IAM role used by a Lambda function that writes to a DynamoDB table. The function also needs to read items from the table. What is the outcome of this policy?

Accepted Answer

The Lambda function can write items but cannot read items. The IAM policy includes an explicit Deny for the `dynamodb:GetItem` action on the table, which overrides any Allow statements due to the explicit deny evaluation logic in AWS IAM. Since the Lambda function assumes a role with this policy, it is denied read access while the Allow for `dynamodb:PutItem` permits write operations. Therefore, the function can write but cannot read items from the DynamoDB table.

Answer

The policy is invalid because it contains both Allow and Deny for the same table

Answer

The Lambda function can both read and write items

Answer

The Lambda function cannot perform any operations on the table

Question 5

A company has a production Amazon DynamoDB table with on-demand capacity. The table experiences occasional throttling due to hot partitions. The operations team wants to implement a solution to identify the specific partition keys causing the throttling. What is the MOST efficient approach?

Accepted Answer

Enable Amazon CloudWatch Contributor Insights for DynamoDB.. Amazon CloudWatch Contributor Insights for DynamoDB is the most efficient solution because it automatically analyzes DynamoDB request metadata to identify the most frequently accessed partition keys, including those causing throttling. It provides near real-time top-N contributor reports without requiring application changes, custom logging, or additional stream processing, making it purpose-built for diagnosing hot partition issues.

Answer

Enable AWS X-Ray tracing on the application and analyze traces.

Answer

Enable VPC Flow Logs and use CloudWatch Logs Insights to query the logs.

Answer

Enable DynamoDB Streams and process the stream records to identify hot keys.

Question 6

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle using AWS DMS. The migration fails with an error indicating that DMS cannot capture changes from the source because the archive log mode is not enabled. What should be done?

Accepted Answer

Enable archive log mode on the source Oracle database.. D is correct because AWS DMS requires archive log mode to be enabled on the source Oracle database for ongoing replication (CDC). Without archive logs, DMS cannot capture the redo data needed to apply changes to the target. Enabling archive log mode ensures the redo logs are preserved and accessible for change data capture.

Answer

Disable ongoing replication and perform a full load only.

Answer

Set up an Oracle Data Guard standby and use it as the source.

Answer

Use AWS Schema Conversion Tool (SCT) to convert the schema.

Question 7

A database administrator notices that an Amazon RDS for MySQL DB instance is using more storage than expected. Which metric should be monitored to troubleshoot storage usage?

Accepted Answer

FreeStorageSpace. FreeStorageSpace is the CloudWatch metric that reports the amount of available storage in bytes on an RDS instance. Monitoring this metric is the direct way to troubleshoot unexpected storage consumption, as it shows how much space remains and helps correlate with data growth, binary logs, or temporary files. A declining FreeStorageSpace trend indicates the need to investigate table growth, log retention, or storage autoscaling settings.

Answer

DatabaseConnections

Answer

ReadIOPS

Answer

NetworkThroughput

Question 8

A financial services company runs a critical application on Amazon RDS for MySQL that processes transactions. The database must maintain ACID compliance and support point-in-time recovery (PITR) with a recovery point objective (RPO) of 5 seconds and recovery time objective (RTO) of 1 minute. The current setup uses a single db.r5.large instance with automated backups enabled (retention period 7 days) and Multi-AZ deployment. During a recent failover test, the failover took 2 minutes, exceeding the RTO. What should the database specialist recommend to meet the RTO requirement?

Accepted Answer

Migrate to a Multi-AZ DB Cluster deployment for RDS for MySQL.. Amazon RDS Multi-AZ DB Cluster deployments use a writer and two readable standbys with a faster failover mechanism (typically under 35 seconds) compared to the classic Multi-AZ instance deployment, which can take 60–120 seconds. This meets the 1-minute RTO while preserving ACID compliance and PITR with 5-second RPO via continuous backup.

Answer

Remove Multi-AZ and rely on automated backups for recovery.

Answer

Configure a cross-Region read replica and promote it during a failure.

Answer

Increase the instance size to db.r5.xlarge to improve failover speed.

Question 9

A company runs an Amazon RDS for Oracle DB instance. The security team wants to ensure that all data in the database is encrypted at rest using a key that the company controls and can audit. Which option should the company choose?

Accepted Answer

Enable encryption at rest using an AWS KMS customer managed key when creating the DB instance.. To encrypt an RDS for Oracle DB instance at rest with a key the company controls and can audit, use an AWS KMS customer managed key. This provides full control over the key lifecycle and auditability via CloudTrail. Oracle TDE with Oracle Wallet does not provide the same level of AWS-integrated control, and SSL/TLS is for data in transit.

Answer

Enable SSL/TLS for all connections to the DB instance.

Answer

Use Oracle Transparent Data Encryption (TDE) with a key stored in Oracle Wallet.

Answer

Enable encryption at rest using an AWS owned key.

Question 10

A company runs a document database using Amazon DocumentDB. They notice that some queries are taking much longer than expected. The explain plan shows a COLLSCAN. Which action would most improve query performance?

Accepted Answer

Create appropriate indexes on the fields used in query filters. Creating appropriate indexes on the fields used in query filters is the most effective action to improve performance because it eliminates the need for a COLLSCAN (collection scan). Increasing instance size (option A) may help but does not address the root cause of missing indexes. Changing read consistency from eventual to strong (option B) affects the freshness of reads, not query performance. Increasing storage (option C) does not improve query speed; it only provides more space for data.

Answer

Increase the instance size to the next tier

Answer

Change the read consistency from eventual to strong

Answer

Increase the storage allocated to the instance

Question 11

A company wants to restrict access to an Amazon DynamoDB table so that only specific IAM users can read and write data. What is the BEST way to achieve this?

Accepted Answer

Create an IAM policy that grants access to the DynamoDB table and attach it to the specific IAM users.. Using an IAM policy attached to specific IAM users is the most precise method to restrict access to a DynamoDB table. Resource-based policies are not supported for DynamoDB (Option A is wrong). VPC endpoints control network traffic but do not restrict which users can access the table (Option D is wrong). DynamoDB Accelerator (DAX) with IAM authentication handles caching and authentication, not table-level access control (Option C is wrong).

Answer

Use a resource-based policy on the DynamoDB table.

Answer

Use DynamoDB Accelerator (DAX) with IAM authentication.

Answer

Create a VPC endpoint for DynamoDB and allow only traffic from that VPC.

Question 12

A company has an Amazon RDS for PostgreSQL instance that is running out of storage. The database is 2 TB in size and growing at 10 GB per day. They need a solution that allows automatic storage scaling with minimal downtime. What should they do?

Accepted Answer

Enable Storage Auto Scaling. Amazon RDS Storage Auto Scaling automatically increases storage when free space drops below a threshold, with no downtime. For a 2 TB database growing at 10 GB/day, this feature dynamically adds storage in predefined increments (e.g., 5 GB, 10 GB, or 10% of current storage) up to the maximum limit, preventing manual intervention. This directly addresses the requirement for automatic scaling with minimal disruption.

Answer

Purchase reserved instances for cost savings

Answer

Create a read replica and promote it

Answer

Take a manual snapshot and restore to a larger instance

Question 13

A company runs an analytics platform that queries billions of rows of sales data. Queries are complex and involve aggregations across multiple dimensions. The data is updated in bulk daily. Which service should be used as the primary data store?

Accepted Answer

Amazon Redshift. Amazon Redshift is the correct choice because it is a fully managed, petabyte-scale data warehouse optimized for complex analytical queries involving aggregations across multiple dimensions. Its columnar storage, massively parallel processing (MPP) architecture, and ability to handle bulk daily updates via COPY commands or INSERT operations make it ideal for querying billions of rows of sales data.

Answer

Amazon DynamoDB

Answer

Amazon Athena

Answer

Amazon RDS for MySQL

Question 14

A company is using Amazon ElastiCache for Redis to cache frequently accessed data from an RDS MySQL database. The cache hit ratio is currently 85%. The operations team notices that during traffic spikes, the cache eviction rate increases significantly, and the database CPU utilization spikes. The cache cluster uses a single r6g.large node. Which THREE actions should the team take to improve performance? (Choose three.)

Accepted Answer

Add more shards to the cluster to increase total memory.. Adding more shards to the cluster increases the total available memory, which reduces the frequency of evictions during traffic spikes. With more memory, the cache can store more data without forcing out existing entries, thereby maintaining a higher cache hit ratio and reducing the load on the RDS MySQL database.

Answer

Reduce the time-to-live (TTL) for cached items to free up memory faster.

Answer

Configure the cache to use lazy loading only for write-through operations.

Question 15

A company has a production Amazon RDS for PostgreSQL Multi-AZ DB instance. The company's security team requires that all database connections use IAM database authentication. The company also needs to ensure that connections from a specific application server are allowed only if the server has a valid IAM role. Which combination of steps should the database administrator take to meet these requirements?

Accepted Answer

Enable IAM database authentication on the RDS instance. Create a database user that matches the IAM role ARN. Grant the application server's IAM role the rds_iam role. Configure the application to generate an authentication token using the IAM role's credentials.. IAM database authentication for RDS PostgreSQL requires mapping IAM roles to database users. Steps: 1) Enable IAM database authentication on the RDS instance. 2) Create a database user that matches the IAM role ARN (the role assumed by the application server). 3) Grant the rds_iam role to the application server's IAM role to allow it to authenticate. 4) Configure the application to generate an authentication token using the IAM role's credentials. Option D is correct because it includes all these steps. Option A is wrong because it uses a password instead of an authentication token. Option B is wrong because it references an IAM user ARN instead of a role ARN. Option C is wrong because it does not enable IAM authentication and uses a password.

Answer

Create a database user with a strong password. Enable IAM database authentication. Assign the application server an IAM policy that allows rds-db:connect. Configure the application to use the password.

Answer

Enable IAM database authentication. Create a database user matching the IAM user ARN. Grant the application server's IAM user the rds_iam role. Configure the application to use an authentication token.

Answer

Enable IAM database authentication. Create a database user that matches the IAM role ARN. Configure the application to use the database master username and password.