DBS-C01 Practice Test 12 — 15 Questions

Question 1

Refer to the exhibit. A developer runs the command against an RDS MySQL instance. The application team reports that the database is experiencing high read latency during peak hours. The database is not currently in Multi-AZ. What is the MOST cost-effective way to reduce read latency?

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

Accepted Answer

Create a read replica in the same region.. Creating a read replica in the same region offloads read traffic from the primary RDS MySQL instance, reducing read latency during peak hours without incurring the cost of a larger instance or a full Aurora migration. Read replicas are asynchronous and can serve SELECT queries, providing a cost-effective scaling solution for read-heavy workloads.

Answer

Enable Multi-AZ to distribute reads to the standby.

Answer

Upgrade the instance to db.r5.2xlarge.

Answer

Migrate to Aurora MySQL with a read replica.

Question 2

Which TWO AWS services can be used to monitor the performance of an Amazon DynamoDB table and send alerts when throttling occurs? (Choose two.)

Accepted Answer

Amazon CloudWatch Alarms. Amazon CloudWatch provides metrics such as ConsumedReadCapacityUnits, ConsumedWriteCapacityUnits, and ThrottledRequests for DynamoDB. You can create CloudWatch Alarms to monitor these metrics and send notifications (e.g., via SNS) when throttling occurs. Therefore, both B (CloudWatch Alarms) and E (CloudWatch) are correct. Option A (Amazon Inspector) is a security assessment service, not a monitoring service. Option C (VPC Flow Logs) captures network traffic, not database performance. Option D (AWS Config) tracks resource configuration changes, not performance metrics.

Answer

Amazon Inspector

Answer

VPC Flow Logs

Answer

AWS Config

Question 3

A company uses Amazon RDS for Oracle with a Multi-AZ deployment for a critical OLTP application. During a recent failover test, they noticed that the application experienced a two-minute downtime. The team wants to reduce downtime to under 30 seconds during automatic failovers. What should they do?

Accepted Answer

Migrate to Amazon Aurora with Multi-AZ and use the Aurora auto-failover feature. Amazon Aurora with Multi-AZ provides faster failover than RDS for Oracle because Aurora uses a shared storage architecture and a cluster endpoint that automatically redirects traffic to the replica within 30 seconds, often in as little as 15 seconds. In contrast, RDS for Oracle Multi-AZ relies on DNS record updates and a standby instance that must be promoted, which typically takes 60–120 seconds. Migrating to Aurora eliminates the DNS propagation delay and the need for storage failover, meeting the sub-30-second requirement.

Answer

Add a read replica to offload reads

Answer

Reduce the DNS TTL value to 5 seconds

Answer

Enable Automatic Failover in the RDS console

Question 4

A gaming company uses Amazon ElastiCache for Redis as a leaderboard for real-time game scores. The leaderboard is updated frequently by millions of users. The application uses sorted sets with player scores. Recently, the leaderboard update latency increased and the cache evictions spiked. The company needs to ensure low-latency updates and high availability. The current setup is a single Redis node. Which design should be implemented?

Accepted Answer

Use a Redis Cluster with multiple shards. Enable AOF persistence and use a read replica for the leaderboard queries.. Redis Cluster with multiple shards distributes the write load across shards, reducing per-node pressure and evictions. Enabling AOF persistence ensures durability, while using a read replica for leaderboard queries offloads read traffic from the primary shard, maintaining low-latency updates. This design provides both horizontal scaling and high availability, addressing the increased update latency and eviction spikes.

Answer

Upgrade to a larger single Redis node instance type to handle the load.

Answer

Replace Redis with DynamoDB for the leaderboard, using a global secondary index on score.

Answer

Use ElastiCache for Redis with cluster mode disabled and enable Multi-AZ.

Question 5

A company is deploying a new MySQL database on Amazon RDS. The database must be highly available and support cross-Region disaster recovery. Which TWO actions should be taken? (Choose two.)

Accepted Answer

Create a cross-region read replica.. A cross-region read replica provides a secondary copy of the database in a different AWS Region, which can be promoted to a standalone primary in a disaster scenario, enabling cross-Region disaster recovery. Option E is correct because Multi-AZ deployment provides automatic failover within a single region by synchronously replicating data to a standby instance in a different Availability Zone, ensuring high availability. Together, these two actions satisfy both high availability (within-region failover) and cross-Region DR requirements.

Answer

Enable encryption at rest using AWS KMS.

Answer

Deploy a Multi-AZ instance in multiple regions.

Answer

Enable automated backups with a retention period of 35 days.

Question 6

A company uses Amazon DynamoDB with auto scaling enabled. They notice that a table's write capacity is frequently throttled during a specific hour each day. The access pattern is uniform across partitions. Which action would resolve the throttling without manual intervention?

Accepted Answer

Increase the minimum provisioned capacity in auto scaling.. When DynamoDB auto scaling is enabled, throttling can occur if the table's write capacity demand spikes faster than auto scaling can increase capacity. The 'minimum provisioned capacity' in the auto scaling policy sets a floor for the capacity units. By increasing this minimum, the table starts with a higher base capacity, reducing the likelihood of throttling during predictable peak hours. Option A is incorrect because DAX is a caching layer for reads, not writes. Option B is incorrect because disabling auto scaling requires manual intervention. Option C is incorrect because table partitioning in DynamoDB is managed automatically based on provisioned capacity; you cannot manually split partitions.

Answer

Enable DynamoDB Accelerator (DAX) to cache writes.

Answer

Disable auto scaling and set a fixed higher capacity.

Answer

Create a larger number of partitions by splitting the table.

Question 7

A company is designing a social media application that requires storing user relationships (follows) and making graph queries like 'mutual friends.' Which database is most suitable?

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 and RDF models, and it uses Gremlin or SPARQL to efficiently traverse relationships like 'mutual friends' in a social media application, making it the ideal choice for graph queries.

Answer

Amazon ElastiCache for Redis

Answer

Amazon DynamoDB

Answer

Amazon RDS for MySQL

Question 8

A startup needs a fully managed, serverless database for a new web application with unpredictable traffic. The application requires ACID transactions and SQL queries. Which AWS database service should they use?

Accepted Answer

Amazon Aurora Serverless v2. Amazon Aurora Serverless v2 is the correct choice because it provides a fully managed, serverless relational database that automatically scales capacity based on application demand, supports ACID transactions, and uses standard SQL queries. It is ideal for unpredictable traffic patterns as it can scale from zero to hundreds of thousands of transactions per minute without manual intervention.

Answer

Amazon Neptune

Answer

Amazon DynamoDB

Answer

Amazon Redshift

Question 9

A company runs a multi-tenant SaaS application on Amazon DynamoDB. Each tenant's data is stored in a separate table named with a tenant-specific prefix (e.g., tenant1_orders, tenant2_orders). The application uses DynamoDB Streams to replicate data to a central analytics table. Recently, the company added a new large tenant that generates 10x more write traffic than any other tenant. The DynamoDB Streams for the large tenant's table is falling behind by several hours, causing stale data in the analytics table. The company has already increased the write capacity of the large tenant's table to 50,000 WCUs, but the streams lag persists. The analytics table is also in DynamoDB and uses a Global Secondary Index (GSI) for querying. The streams processing Lambda function performs simple transformations and writes to the analytics table. The Lambda function is not throttled. Which action would resolve the streams lag?

Accepted Answer

Enable DynamoDB on-demand mode for the large tenant's table to allow automatic scaling of stream shards.. DynamoDB Streams shards are directly tied to the physical partitions of the table. When a table is in provisioned mode, the number of stream shards is fixed and determined by the table's partitions, which cannot scale independently. Enabling on-demand mode allows DynamoDB to automatically split partitions and thus increase the number of stream shards, enabling higher stream throughput to keep up with the large tenant's write volume. This directly addresses the root cause of the streams lag without requiring manual partition management.

Answer

Remove the GSI from the analytics table to reduce write amplification.

Answer

Increase the Lambda function's reserved concurrency to the maximum.

Answer

Increase the write capacity of the large tenant's table to 100,000 WCUs.

Question 10

A company runs a time-series application that collects sensor data from millions of IoT devices. The data is written in batches every minute and queried to generate hourly, daily, and monthly aggregates. The database must support high ingestion rates and efficient storage. Which database service is most appropriate?

Accepted Answer

Amazon Timestream. Amazon Timestream is purpose-built for time-series data, offering a serverless architecture that automatically scales to handle high ingestion rates from millions of IoT devices. It optimizes storage by separating recent data (in memory) from historical data (in a magnetic store), and its built-in aggregation functions (e.g., `BIN`, `DATE_BIN`) efficiently compute hourly, daily, and monthly aggregates without manual partitioning or indexing.

Answer

Amazon DynamoDB with TTL

Answer

Amazon Redshift

Answer

Amazon RDS for PostgreSQL

Question 11

A company is building a real-time chat application that requires storing messages with a maximum of 10,000 characters per message. The application needs sub-millisecond latency for reads and writes. The data must be durable and replicated across three Availability Zones. The development team wants to minimize operational overhead. Which AWS database service is most appropriate?

Accepted Answer

Amazon DynamoDB with DAX. Amazon DynamoDB with DAX is the most appropriate choice because it provides single-digit millisecond latency for reads and writes, supports up to 400 KB per item (easily accommodating 10,000 characters), and offers built-in replication across three Availability Zones for durability. DAX (DynamoDB Accelerator) further reduces read latency to sub-millisecond by serving as an in-memory cache, while DynamoDB itself handles write durability and replication automatically, minimizing operational overhead.

Answer

Amazon ElastiCache for Redis with replication

Answer

Amazon RDS for PostgreSQL with Multi-AZ

Answer

Amazon Aurora MySQL with Multi-AZ

Question 12

A database specialist needs to monitor the resource utilization of Amazon RDS DB instances. Which AWS service provides OS-level metrics such as memory, disk, and CPU usage?

Accepted Answer

Amazon RDS Enhanced Monitoring. Amazon RDS Enhanced Monitoring provides OS-level metrics (e.g., memory, disk, CPU usage) by running an agent on the RDS host and delivering logs to CloudWatch Logs. This is the only service that exposes hypervisor-level and guest OS metrics for RDS instances, enabling granular troubleshooting of resource contention.

Answer

Amazon RDS Performance Insights

Answer

Amazon CloudWatch

Answer

AWS CloudTrail

Question 13

A company is deploying a new application using Amazon RDS for PostgreSQL. They require high availability with automatic failover and the ability to offload read traffic. Which TWO features should they enable? (Choose two.)

Accepted Answer

Multi-AZ deployment. Multi-AZ deployment (Option A) provides high availability by automatically provisioning and maintaining a synchronous standby replica in a different Availability Zone. If the primary DB instance fails, Amazon RDS automatically fails over to the standby, ensuring minimal downtime. Read replicas (Option B) offload read traffic by creating asynchronous copies of the database that can serve read queries, reducing load on the primary instance.

Answer

Performance Insights

Answer

Global Database

Answer

Auto Scaling for read replicas

Question 14

A company uses Amazon DynamoDB global tables for a multi-region application. They notice that writes in one region are not appearing in another region after several minutes. What should they check first?

Accepted Answer

Check the ReplicationLatency metric in Amazon CloudWatch. The ReplicationLatency metric in CloudWatch directly measures the delay between a write in one region and its replication to another region in DynamoDB global tables. This is the most relevant metric to diagnose replication delays. Option B (auto scaling) affects capacity provisioning, not replication timing. Option C (DynamoDB Streams) are enabled by default for global tables to facilitate replication, but checking the metric is the immediate next step if delays are observed. Option D (table size) does not directly cause replication delays; replication is asynchronous and not size-dependent.

Answer

Verify that auto scaling is configured identically in both regions

Answer

Ensure DynamoDB Streams are enabled on the table

Answer

Check the table size in both regions

Question 15

A financial services company is using Amazon DynamoDB to store customer transaction data. The compliance team requires that all data be encrypted at rest using a customer-managed AWS KMS key, and that access to the key be auditable via AWS CloudTrail. Additionally, the security team wants to ensure that DynamoDB can only be accessed from within the VPC using a VPC endpoint. Which combination of steps should the company take to meet these requirements?

Accepted Answer

Enable server-side encryption with a customer-managed KMS key and create an interface VPC endpoint for DynamoDB.. Option C. To meet the encryption requirement, the company must use a customer-managed KMS key, not an AWS managed key. For VPC-only access, DynamoDB supports interface VPC endpoints (via AWS PrivateLink), which provide private connectivity. Option C correctly uses a customer-managed KMS key and an interface VPC endpoint. Option D is incorrect because it uses an AWS managed KMS key. Option A is incorrect because CloudHSM is unnecessary and VPC peering is not the correct method. Option B is incorrect because a NAT gateway still routes traffic over the internet.

Answer

Use a CloudHSM key for encryption and create a VPC peering connection to DynamoDB.

Answer

Enable server-side encryption with a customer-managed KMS key and route all traffic through a NAT gateway.

Answer

Use AWS managed KMS key and a gateway VPC endpoint for DynamoDB.