DBS-C01 Practice Test 9 — 10 Questions

Question 1

A company is designing a document management system using Amazon S3 and needs to store metadata such as document ID, owner, creation date, and tags. The metadata must be searchable with low latency, supporting queries like 'Find all documents owned by user X with tag Y created after date Z'. Which AWS database service is most suitable for storing and querying this metadata?

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

Accepted Answer

Amazon DynamoDB with a GSI on (owner, creation_date) and a filter on tags.. Amazon DynamoDB is the most suitable choice because it provides single-digit millisecond latency for queries at any scale, which meets the low-latency search requirement. By creating a Global Secondary Index (GSI) on (owner, creation_date), you can efficiently query documents by owner and date range, and then apply a filter expression on tags to narrow results. This schema avoids the overhead of joins and normalization, making it ideal for high-throughput metadata lookups.

Answer

Amazon Redshift Spectrum querying metadata stored in S3 as CSV.

Answer

Amazon RDS for PostgreSQL with a normalized schema.

Answer

Amazon ElastiCache for Redis with sorted sets for tags.

Question 2

A company runs a time-series application that records sensor data every second. The data volume is 500 GB per month and grows continuously. They need to query the last 30 days of data frequently and older data rarely. Which database design is MOST appropriate?

Accepted Answer

Amazon Timestream. Amazon Timestream is purpose-built for time-series data, automatically storing recent data in memory for fast queries and moving older data to a cost-optimized store. This matches the workload of frequent queries on the last 30 days and rare queries on older data, with continuous growth at 500 GB/month.

Answer

Amazon RDS for PostgreSQL with partitioning

Answer

Amazon DynamoDB with TTL

Answer

Amazon S3 with Athena and partitioning

Question 3

A company needs to audit all SQL queries executed on an Amazon RDS for PostgreSQL instance. Which feature should the company enable?

Accepted Answer

pgAudit extension. PgAudit (PostgreSQL Audit Extension) is the native, supported way to log all SQL queries on Amazon RDS for PostgreSQL. It provides detailed session and object audit logging via the shared_preload_libraries parameter, capturing every executed statement without requiring external tools or additional infrastructure.

Answer

Advanced Audit

Answer

Database Activity Streams

Answer

Fine-Grained Auditing

Question 4

A company is running a critical application on Amazon DynamoDB. The table has a partition key of 'user_id' and a sort key of 'timestamp'. The application frequently queries for all items for a given user within a date range. The read capacity is often throttled during peak hours. Which THREE steps should the database specialist take to resolve the throttling?

Accepted Answer

Enable DynamoDB adaptive capacity to automatically adjust throughput. DynamoDB adaptive capacity automatically manages throughput to accommodate uneven access patterns, such as when a single 'user_id' partition receives more reads than provisioned. It allows the table to absorb throttling by redistributing unused capacity from other partitions, which directly addresses the peak-hour throttling without manual intervention.

Answer

Change the partition key to 'timestamp' to improve read distribution

Answer

Decrease the provisioned write capacity units (WCU) to free up resources for reads

Question 5

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 6

A social media application stores user posts in an Amazon RDS for PostgreSQL instance. The application experiences a sudden spike in read traffic during peak hours, causing database bottlenecks. The team needs to improve read scalability without changing the application code. Which solution is MOST cost-effective?

Accepted Answer

Use Amazon RDS for PostgreSQL Read Replicas. Amazon RDS for PostgreSQL Read Replicas allow you to offload read traffic from the primary DB instance to one or more read-only replicas, improving read scalability without any application code changes. This is the most cost-effective solution as it leverages the existing PostgreSQL engine and requires only minimal additional compute and storage costs for the replicas.

Answer

Migrate to Amazon DynamoDB with DAX

Answer

Enable Multi-AZ on the RDS instance

Answer

Use Amazon ElastiCache to cache query results

Question 7

An IAM policy is attached to a user to allow read access to the Orders table in DynamoDB. The user reports that a GetItem call for an order returns an 'AccessDeniedException'. What is the likely cause?

Accepted Answer

The user must specify a projection expression in the GetItem request to include only 'order_id' and 'status' attributes.. When an IAM policy uses the `dynamodb:Attributes` condition key to restrict access to specific attributes (e.g., `order_id` and `status`), the user must include a `ProjectionExpression` in the `GetItem` request that explicitly lists only those allowed attributes. Without the projection expression, DynamoDB attempts to return all attributes, which triggers an `AccessDeniedException` because the policy denies access to attributes not listed in the condition.

Answer

The user does not have permissions to perform GetItem on the Orders table.

Answer

The resource ARN is incorrect; it should include the wildcard for the table.

Answer

The condition key 'dynamodb:Attributes' restricts access to only two attributes, but the user can still get all attributes.

Question 8

A company is designing a database for a social media application that requires storing user profiles, posts, and follower relationships. The application needs low-latency queries for user timelines and social graph traversals. Which TWO AWS database services should the database specialist consider? (Choose TWO.)

Accepted Answer

Amazon Neptune. Amazon Neptune is a fully managed graph database service optimized for storing and querying highly connected data, such as social graphs. It supports property graph and RDF models, enabling low-latency traversals of follower relationships and user timelines using Gremlin or SPARQL queries.

Answer

Amazon Timestream

Answer

Amazon Redshift

Answer

Amazon RDS for MySQL

Question 9

A company uses Amazon DynamoDB for a gaming leaderboard. The application updates scores frequently. Reads must be strongly consistent, and writes must be optimized for cost. Which table design minimizes cost while meeting consistency requirements?

Accepted Answer

Use Amazon DynamoDB Accelerator (DAX) for caching.. Amazon DynamoDB Accelerator (DAX) provides an in-memory cache that supports strongly consistent reads, which meets the application's requirement for strongly consistent reads. By caching frequently accessed leaderboard data, DAX reduces the number of read capacity units consumed from the DynamoDB table, thereby lowering read costs. Writes are still performed directly on the DynamoDB table, and DAX does not affect write costs, so the design optimizes overall cost while maintaining consistency.

Answer

Use eventually consistent reads with a conditional write.

Answer

Store scores in Amazon S3 and use S3 Select for reads.

Answer

Use DynamoDB Streams to replicate reads to a separate table.

Question 10

A company is using Amazon RDS for MySQL and notices that the Read IOPS metric is consistently high during business hours. The application is read-heavy. Which configuration change would most likely reduce Read IOPS?

Accepted Answer

Create one or more read replicas and redirect read traffic to them.. Creating read replicas offloads read queries from the primary DB instance to replica instances, directly reducing the number of read I/O operations on the primary. Since the application is read-heavy and Read IOPS is high during business hours, distributing read traffic to replicas alleviates the I/O bottleneck on the primary instance without requiring a larger instance or storage changes.

Answer

Add a Multi-AZ standby instance.

Answer

Increase the DB instance size to a larger instance type.

Answer

Enable storage Auto Scaling on the RDS instance.