DBS-C01 Workload-Specific Database Design Practice Test 21 — 15 Questions

Question 1

A company wants to run a graph database for a social network application. The data model involves users, posts, comments, and likes, with many-to-many relationships. Which AWS database service is most appropriate?

Accepted Answer

Amazon Neptune. Amazon Neptune is a fully managed graph database service optimized for highly connected data. DynamoDB is NoSQL but not graph. RDS is relational, which can model graphs but with complex queries. DocumentDB is document-based.

Answer

Amazon RDS for PostgreSQL

Answer

Amazon DocumentDB

Answer

Amazon DynamoDB

Question 2

A company runs a reporting application that queries an Amazon RDS for PostgreSQL database. The queries are complex and take a long time to run, causing performance degradation on the primary instance. The team wants to improve query performance without affecting the transactional workload. Which solution should they use?

Accepted Answer

Create one or more read replicas and direct reporting queries to them. Read replicas offload read queries from the primary. Amazon RDS for PostgreSQL supports read replicas, and the reporting application can be configured to connect to the replica. Option A (increase instance) helps but may not be cost-effective. Option C (Aurora) is an alternative but not necessary. Option D (ElastiCache) is for caching, not complex queries.

Answer

Increase the instance size of the primary database

Answer

Migrate to Amazon RDS for MySQL and use Multi-AZ

Answer

Use Amazon ElastiCache to cache the results of complex queries

Question 3

A company uses Amazon DynamoDB to store order data. The table has a primary key (OrderID) and a Global Secondary Index (GSI) on CustomerID. The application often queries for all orders of a customer sorted by order date. The GSI projects only the keys. The queries are slow. What should the team do to improve query performance? (Choose two.)

Accepted Answer

Modify the GSI to include OrderDate as a sort key. Option B: Adding a sort key (OrderDate) to the GSI allows sorting natively. Option D: If the GSI projects only keys, each query results in a fetch from the base table (expensive). Changing projection to INCLUDE or ALL avoids the extra fetch. Option A would increase write costs unnecessarily. Option C may not help if the GSI is inefficient. Option E is not directly related.

Answer

Enable DynamoDB Accelerator (DAX) for the table

Answer

Increase the read capacity of the GSI

Answer

Use a Local Secondary Index (LSI) instead of a GSI

Question 4

A company runs an e-commerce application on Amazon RDS for MySQL. The application experiences read-heavy traffic during flash sales. The development team wants to offload read traffic without changing the application code. Which solution should be used?

Accepted Answer

Create an RDS Read Replica and point read traffic to the replica endpoint.. Option C is correct because Amazon RDS Read Replicas allow offloading read traffic from the primary DB instance without application changes. Option A is wrong because DynamoDB Accelerator (DAX) is for DynamoDB, not RDS. Option B is wrong because Multi-AZ is for high availability, not read scaling. Option D is wrong because ElastiCache requires application changes to use caching logic.

Answer

Implement an Amazon ElastiCache cluster and update the application to cache queries.

Answer

Configure Multi-AZ deployment for the RDS instance.

Answer

Use DynamoDB Accelerator (DAX) in front of the RDS instance.

Question 5

A financial services company uses Amazon DynamoDB to store transaction records. The table has a partition key of 'AccountId' and a sort key of 'TransactionDate'. The company needs to run analytical queries that aggregate transactions by account and month. Currently, queries are slow due to full table scans. Which design change will improve query performance most effectively?

Accepted Answer

Create a Global Secondary Index (GSI) with partition key AccountId and sort key Month.. Option B is correct because creating a Global Secondary Index (GSI) with AccountId as partition key and Month as sort key allows efficient querying without scans. Option A is wrong because changing the sort key to Month loses the ability to query by exact date. Option C is wrong because enabling DynamoDB Streams does not improve query performance. Option D is wrong because DynamoDB Accelerator (DAX) speeds up reads but does not change the query pattern.

Answer

Add DynamoDB Accelerator (DAX) to the table.

Answer

Change the table's sort key from TransactionDate to Month.

Answer

Enable DynamoDB Streams and process the stream with AWS Lambda to pre-aggregate results.

Question 6

A company needs to migrate an on-premises PostgreSQL database to Amazon Aurora PostgreSQL. The database is 2 TB in size and has a 24/7 uptime requirement. Which AWS service should be used to perform the migration with minimal downtime?

Accepted Answer

AWS Database Migration Service (DMS). Option B is correct because AWS Database Migration Service (DMS) supports minimal-downtime migrations using change data capture (CDC). Option A is wrong because S3 is for storage, not database migration. Option C is wrong because the AWS Schema Conversion Tool (SCT) converts schemas but does not perform data migration. Option D is wrong because pg_dump requires downtime for consistent export.

Answer

AWS Schema Conversion Tool (SCT)

Answer

AWS S3

Answer

pg_dump and pg_restore

Question 7

A company uses Amazon RDS for MySQL with Multi-AZ. During a recent failover test, the database experienced a 5-minute write outage. The application can tolerate up to 1 minute of downtime. Which solution should be used to reduce the failover time?

Accepted Answer

Migrate to Amazon Aurora MySQL.. Option D is correct because Amazon Aurora MySQL provides faster failover (typically under 30 seconds) due to its shared storage architecture. Option A is wrong because modifying the DNS TTL may help but does not reduce the failover time significantly. Option B is wrong because RDS Proxy helps with connection pooling, not failover speed. Option C is wrong because Multi-AZ already provides automatic failover, but failover time is typically 1-2 minutes for RDS.

Answer

Use Amazon RDS Proxy between the application and the database.

Answer

Enable automatic failover on the Multi-AZ deployment.

Answer

Decrease the DNS TTL on the RDS endpoint.

Question 8

A company is designing a database for a social media application that stores user posts. Each post can have multiple tags. The workload requires low-latency queries to find all posts with a specific tag. Which database design is most suitable?

Accepted Answer

Amazon DynamoDB with a Global Secondary Index on the tag attribute.. Option A is correct because Amazon DynamoDB with a GSI on the tag attribute allows fast queries by tag. Option B is wrong because RDS for MySQL with a normalized schema would require joins, which are slower for this use case. Option C is wrong because ElastiCache is a cache, not a primary data store. Option D is wrong because Neptune is for graph data, not for this simple tag lookup.

Answer

Amazon ElastiCache for Memcached storing posts and tags as key-value pairs.

Answer

Amazon RDS for MySQL with a normalized schema and JOIN queries.

Answer

Amazon Neptune with a graph model for tags and posts.

Question 9

A company uses Amazon DynamoDB to store session data for a web application. The table has a partition key of 'SessionId'. The company wants to automatically expire sessions after 1 hour. Which feature should be used?

Accepted Answer

DynamoDB Time to Live (TTL). Option B is correct because DynamoDB TTL automatically expires items after a specified timestamp. Option A is wrong because DynamoDB Streams captures changes but does not expire items. Option C is wrong because the application would need to scan and delete, which is inefficient. Option D is wrong because Global Tables are for multi-region replication, not expiration.

Answer

DynamoDB Global Tables

Answer

AWS Lambda function that scans the table every hour and deletes old items.

Answer

DynamoDB Streams

Question 10

A company runs an Oracle database on Amazon RDS. The database is used by multiple applications, and the company needs to capture all data modification language (DML) changes for auditing. Which solution should be used?

Accepted Answer

Use AWS DMS with change data capture (CDC) to stream changes to Amazon S3.. Option D is correct because AWS DMS with CDC and stream to S3 allows capturing DML changes and storing them for auditing. Option A is wrong because RDS does not support Oracle Flashback. Option B is wrong because RDS does not support Oracle Audit Vault. Option C is wrong because CloudTrail does not capture database-level DML.

Answer

Use AWS CloudTrail to capture database events.

Answer

Enable Oracle Flashback and store the flashback logs.

Answer

Install Oracle Audit Vault on the RDS instance.

Question 11

A company uses Amazon Aurora MySQL for a SaaS application. Each tenant has a separate database. The company wants to implement a centralized monitoring solution that collects performance metrics from all tenant databases. The solution should be cost-effective and require minimal overhead. Which approach should be used?

Accepted Answer

Use Amazon CloudWatch Agent to collect custom metrics from each Aurora instance and aggregate in CloudWatch.. Option C is correct because Amazon CloudWatch Agent installed on each Aurora instance can collect custom metrics, but more efficiently, Aurora publishes Performance Insights metrics to CloudWatch. Option A is wrong because a single RDS instance cannot host multiple databases for isolation. Option B is wrong because DMS is for data migration, not monitoring. Option D is wrong because a Lambda function querying each database would create overhead.

Answer

Use AWS DMS to continuously replicate metrics to a central RDS instance.

Answer

Consolidate all tenants into a single RDS MySQL instance and use separate schemas.

Answer

Run an AWS Lambda function that queries each database's performance_schema every minute and stores results in S3.

Question 12

A company needs to store JSON documents that are up to 10 KB in size. The documents are accessed by a primary key, and the company requires single-digit millisecond latency. Which database service should be used?

Accepted Answer

Amazon DynamoDB. Option A is correct because DynamoDB is a key-value and document database that provides single-digit millisecond latency at scale. Option B is wrong because RDS for MySQL can store JSON but may not provide consistent single-digit ms latency under load. Option C is wrong because Neptune is for graph data. Option D is wrong because S3 has higher latency for small objects.

Answer

Amazon Neptune

Answer

Amazon S3

Answer

Amazon RDS for MySQL with JSON data type

Question 13

A company is designing a database for an IoT application that ingests millions of sensor readings per second. The data is time-series and is queried to generate reports on average temperature over the last hour. Which TWO database solutions are most suitable for this workload?

Accepted Answer

Amazon DynamoDB with time-series data model and TTL. Option B (Timestream) is a purpose-built time-series database for IoT data. Option D (DynamoDB with TTL and optimized access pattern) can also handle time-series data if designed properly with partition key and sort key. Option A is wrong because Neptune is for graph data. Option C is wrong because ElastiCache is a cache, not a primary store for long-term data. Option E is wrong because RDS is not optimized for high-ingestion time-series.

Answer

Amazon Neptune

Answer

Amazon RDS for PostgreSQL

Answer

Amazon ElastiCache for Redis

Question 14

A company is migrating a large Oracle data warehouse to Amazon Redshift. The source database has many complex stored procedures, views, and joins. Which THREE actions should the company take during the migration?

Accepted Answer

Use the AWS Schema Conversion Tool (SCT) to convert stored procedures.. Option A is correct because Redshift is columnar and may require denormalization. Option B is correct because the AWS Schema Conversion Tool (SCT) can convert Oracle stored procedures to Redshift SQL. Option D is correct because Redshift is optimized for star schema (fact and dimension tables). Option C is wrong because Redshift does not support indexes like Oracle. Option E is wrong because Redshift does not support triggers.

Answer

Migrate triggers as they are in Redshift.

Answer

Recreate all indexes from Oracle in Redshift.

Question 15

A company runs a web application that uses Amazon RDS for MySQL. The database frequently experiences high CPU utilization due to many concurrent connections. The application uses connection pooling at the application layer. Which TWO approaches can reduce CPU load on the database?

Accepted Answer

Use Amazon RDS Proxy to manage database connections.. Option A is correct because RDS Proxy manages connection pooling, reducing the overhead of establishing connections. Option D is correct because caching frequent read queries with ElastiCache reduces database load. Option B is wrong because increasing instance size may help but is not the most targeted solution. Option C is wrong because read replicas help with read scaling, not CPU due to connections. Option E is wrong because Multi-AZ does not reduce CPU load.

Answer

Enable Multi-AZ to distribute the load.

Answer

Create read replicas to offload read traffic.

Answer

Increase the DB instance size to a larger instance type.