DBS-C01 Practice Test 47 — 15 Questions

Question 1

A company is experiencing high read latency on their Amazon RDS for MySQL Multi-AZ DB instance. The application performs many small, random reads. Which configuration change would most likely reduce the read latency without incurring additional compute costs?

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

Accepted Answer

Enable Multi-AZ DB cluster deployment with two readable standby instances and route read traffic to the standby.. The Multi-AZ DB cluster deployment for Amazon RDS includes two readable standby instances. By routing read traffic to these standbys, the load on the primary is reduced, which can decrease read latency without additional compute costs since the standbys are already provisioned. Option A is incorrect because increasing allocated storage primarily improves I/O throughput for sequential operations but may not significantly reduce latency for many small random reads. Option B is incorrect because Performance Insights is a monitoring tool that helps identify performance bottlenecks but does not directly reduce read latency. Option D is incorrect because increasing the instance size (e.g., from db.r5.large to db.r5.xlarge) would incur additional compute costs.

Answer

Increase the allocated storage size to improve I/O throughput.

Answer

Enable Performance Insights to monitor and optimize queries.

Answer

Increase the instance size from db.r5.large to db.r5.xlarge.

Question 2

A developer is writing an AWS Lambda function that needs to access a Secrets Manager secret to retrieve database credentials. The Lambda function has an IAM role. Which action must be allowed in the IAM policy?

Accepted Answer

secretsmanager:GetSecretValue. The Lambda function must call secretsmanager:GetSecretValue to retrieve the secret. Option A (kms:Decrypt) may be necessary if the secret is encrypted with a KMS key, but it is not the primary action. Option B (secretsmanager:PutSecretValue) is for updating secrets, not reading. Option C (secretsmanager:ListSecrets) only lists secret names, not the actual values.

Answer

kms:Decrypt

Answer

secretsmanager:PutSecretValue

Answer

secretsmanager:ListSecrets

Question 3

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 4

A company is using Amazon Redshift for data warehousing. The data engineering team notices that queries are taking longer than expected. The cluster has two nodes of type dc2.large. The database specialist checks the system tables and finds that many queries are using the disk for temporary storage. Which action should the specialist take to improve query performance?

Accepted Answer

Upgrade the cluster to a node type with more memory, such as ra3.xlplus.. Disk spill to temporary storage indicates insufficient memory per node. Upgrading from dc2.large (∼15 GB RAM) to ra3.xlplus (∼32 GB RAM) doubles per-node memory, reducing disk spill and improving query performance. Option A is incorrect because distribution keys improve data distribution, not memory. Option B is incorrect because concurrency scaling manages concurrent queries, not per-query memory. Option C is incorrect because adding a node increases total cluster memory but per-node memory stays the same; disk spill occurs per node, so the problem persists.

Answer

Add distribution keys to the tables to improve data distribution.

Answer

Enable concurrency scaling to offload queries to additional clusters.

Answer

Increase the number of nodes to three to distribute the workload.

Question 5

A data analyst reports that a nightly ETL job to Amazon Redshift is failing with timeout errors shown in the exhibit. The cluster is a dc2.large with 2 nodes. The ETL job inserts large volumes of data. What is the most likely cause?

Accepted Answer

The cluster has insufficient disk space for the data load.. The dc2.large node type has a fixed storage limit of 160 GB per node (320 GB total for 2 nodes). When an ETL job inserts large volumes of data and the cluster runs out of disk space, Redshift cannot write new rows, causing the load to hang and eventually time out. Insufficient disk space is a common cause of timeout errors during bulk inserts because the database cannot complete the write operations.

Answer

The cluster has reached the maximum number of connections.

Answer

The workload manager (WLM) queue timeout is too low.

Answer

The security group is blocking inbound traffic from the ETL server.

Question 6

A company's DynamoDB table uses provisioned capacity and has a global table for disaster recovery. Write requests to the replica region are failing with ProvisionedThroughputExceededException even though the replica table shows low consumed capacity. What is the MOST likely cause?

Accepted Answer

The replica table's write capacity is insufficient for replication writes. In DynamoDB global tables, writes to the replica region consume write capacity units (WCUs) on the replica table. If the provisioned write capacity on the replica table is insufficient to handle the replication traffic, the replica will throttle incoming write requests with a ProvisionedThroughputExceededException, even if the consumed capacity appears low because throttling occurs before the write is counted. Option C correctly identifies this cause. Option A is incorrect because auto-scaling adjusts capacity over time but does not directly cause throttling. Option B is incorrect because burst capacity provides short-term flexibility; sustained throttling is due to insufficient capacity, not burst exhaustion. Option D is incorrect because DAX is an in-memory cache for reads and does not affect write operations.

Answer

Auto-scaling is disabled on the replica table

Answer

The replica table is exhausting its burst capacity

Answer

DAX is enabled on the replica table

Question 7

A company uses Amazon RDS for SQL Server with Multi-AZ deployment. The security team wants to ensure that all database connections use SSL/TLS encryption. Which TWO actions should the database specialist take to enforce SSL connections? (Choose two.)

Accepted Answer

Create a server-level trigger that requires SSL for all logins.. SQL Server allows you to create a server-level DDL trigger that checks the login event and enforces SSL by examining the `@@OPTIONS` or `encrypt_option` in `sys.dm_exec_connections`. This is a supported method to force SSL for all connections to an RDS for SQL Server instance. Option E is correct because setting the `rds.force_ssl` parameter to 1 in the DB parameter group is the native RDS mechanism to enforce SSL/TLS for all connections to the DB instance.

Answer

Use the RDS Console to enable 'Force SSL' on the DB instance.

Answer

Modify the DB parameter group to set 'require_secure_transport' to ON.

Answer

Add an inbound rule to the security group that only allows traffic on port 1433 from IP addresses that use SSL.

Question 8

A company is using Amazon DynamoDB with global tables. The application writes to a table in the us-east-1 region. The database administrator notices that updates made in us-east-1 are not appearing in the replica table in eu-west-1. What is the most likely cause?

Accepted Answer

DynamoDB Streams are not enabled on the table.. DynamoDB global tables rely on DynamoDB Streams to replicate changes. If streams are not enabled, updates will not be replicated to other regions. Option B is incorrect because DynamoDB does not have a configurable replication delay; replication is near real-time. Option C is incorrect because point-in-time recovery is a backup feature and does not affect replication. Option D is incorrect because insufficient IAM permissions would typically cause error messages or failures, not a silent lack of replication.

Answer

The replication delay is set too high.

Answer

Point-in-time recovery is not enabled on the replica table.

Answer

The IAM role for replication does not have sufficient permissions.

Question 9

A company is migrating an on-premises MongoDB database to AWS. The database stores JSON documents for a content management system. The workload requires read-after-write consistency and automatic scaling. Which AWS database service is MOST appropriate?

Accepted Answer

Amazon DocumentDB. Amazon DocumentDB is the most appropriate choice because it is a fully managed, MongoDB-compatible document database that natively stores JSON documents, supports read-after-write consistency via its default session consistency model, and provides automatic scaling of storage (up to 64 TB) and compute resources. It directly replaces on-premises MongoDB workloads without requiring schema changes or application rewrites, making it ideal for a content management system.

Answer

Amazon ElastiCache for Redis

Answer

Amazon DynamoDB

Answer

Amazon RDS for PostgreSQL

Question 10

What is the purpose of the 'TimeToLiveSpecification' in this template?

Accepted Answer

It enables DynamoDB to automatically delete items after the specified timestamp. The 'TimeToLiveSpecification' in an AWS DynamoDB CloudFormation template enables DynamoDB's Time to Live (TTL) feature, which automatically deletes items when the current time exceeds the epoch timestamp value stored in the specified attribute (e.g., 'expire_time'). This is a cost-effective way to manage data retention without requiring custom delete logic or additional write capacity.

Answer

It enforces that the 'expire_time' attribute must be unique

Answer

It automatically updates the 'expire_time' attribute when an item is read

Answer

It creates a backup of items that have expired

Question 11

A company is designing a database for an IoT application that ingests sensor data from thousands of devices. Each device sends a reading every minute. The data includes device_id, timestamp, temperature, humidity, and pressure. The application needs to store this data and support queries that retrieve all readings for a specific device within a time range. The company expects high write throughput and moderate read frequency. The data must be stored with high durability. Which TWO database designs are appropriate for this workload? (Choose TWO.)

Accepted Answer

Use Amazon DynamoDB with device_id as partition key and timestamp as sort key.. DynamoDB's partition key (device_id) and sort key (timestamp) design allows efficient retrieval of all readings for a specific device within a time range using a Query operation with a KeyConditionExpression on the sort key. This schema supports high write throughput by distributing writes across partitions based on device_id, and DynamoDB's multi-AZ replication provides high durability.

Answer

Use Amazon DynamoDB with device_id as partition key and store all readings for a device as a list attribute in a single item, updating the list every minute.

Answer

Use Amazon S3 to store compressed JSON files per device per hour, and query using Amazon Athena.

Answer

Use Amazon RDS for MySQL with a single table and index on device_id and timestamp.

Question 12

A company is using Amazon DynamoDB with auto scaling enabled. Despite auto scaling, the application is still experiencing throttling during traffic spikes. Which THREE actions should the company take to resolve this issue? (Choose THREE.)

Accepted Answer

Implement exponential backoff in the application code. Exponential backoff (A) is a best practice to retry throttled requests gracefully, reducing retry storms. DAX (B) caches read-heavy workloads, reducing read capacity unit consumption and mitigating hot key issues. Global tables (C) distribute write traffic across multiple regions, alleviating write throttling. Option D (on-demand capacity) could help but may be cost-prohibitive and does not address hot keys. Option E (disable auto scaling) would worsen throttling by fixing capacity. Therefore, A, B, and C are correct.

Answer

Switch to on-demand capacity mode

Answer

Disable auto scaling and set fixed capacity

Question 13

A company uses Amazon Redshift for data warehousing. The security team requires that all data loaded into the cluster be encrypted at rest using a customer-managed KMS key. The cluster is currently unencrypted. What is the most efficient way to achieve this requirement with minimal data loss?

Accepted Answer

Unload the data from the existing cluster to S3, create a new encrypted cluster using the KMS key, and reload the data from S3.. An existing unencrypted Redshift cluster cannot be encrypted in place. The only way to achieve encryption using a customer-managed KMS key is to unload the data to S3, create a new encrypted cluster with the desired KMS key, and reload the data. Options B, C, and D are incorrect because Redshift does not support enabling encryption on an existing cluster, modifying an existing cluster to enable encryption, or adding encryption to an unencrypted snapshot.

Answer

Change the cluster parameter group to enable encryption.

Answer

Modify the cluster and enable encryption in the Redshift console.

Answer

Take a snapshot of the cluster, copy the snapshot with encryption, and restore from the encrypted snapshot.

Question 14

A company is migrating an on-premises Oracle database to Amazon Aurora PostgreSQL. The database has several stored procedures that use Oracle-specific PL/SQL. The team needs to minimize manual code changes. Which AWS service or tool should be used to automate the conversion of the stored procedures?

Accepted Answer

AWS Schema Conversion Tool (AWS SCT). The AWS Schema Conversion Tool (AWS SCT) is the correct choice because it automates the conversion of Oracle PL/SQL stored procedures to PostgreSQL PL/pgSQL, minimizing manual code changes. Option B (Amazon Aurora PostgreSQL native compatibility) does not automatically convert Oracle PL/SQL; it only supports some PostgreSQL features. Option C (AWS DMS) handles data migration, not schema or code conversion. Option D (manual rewrite) is not automated and contradicts the requirement to minimize manual changes.

Answer

Amazon Aurora PostgreSQL native compatibility

Answer

AWS Database Migration Service (AWS DMS)

Answer

Manual rewrite using PostgreSQL PL/pgSQL

Question 15

A database specialist notices that an RDS MySQL instance's FreeableMemory metric is consistently below 100 MB. Which monitoring tool should be used to identify the queries consuming the most memory?

Accepted Answer

Performance Insights. Performance Insights provides detailed query-level performance metrics, including memory consumption per query, which helps identify the queries consuming the most memory on an RDS MySQL instance. Option B is incorrect because Amazon S3 access logs record requests made to S3 buckets, not RDS memory usage. Option C is incorrect because AWS CloudTrail logs API calls for auditing, not database memory. Option D is incorrect because CloudWatch Logs can store logs but do not provide query-level memory analysis.

Answer

Amazon S3 access logs

Answer

AWS CloudTrail

Answer

CloudWatch Logs