DBS-C01 Practice Test 20 — 15 Questions

Question 1

An e-commerce platform uses Amazon DynamoDB for a shopping cart table with partition key 'user_id' and sort key 'product_id'. The table experiences throttled write requests during flash sales. The access pattern includes reading the entire cart at checkout. Which design change would improve write performance without changing the read pattern?

Accepted Answer

Enable DynamoDB Adaptive Capacity and ensure the table uses on-demand capacity mode. Option C is correct because DynamoDB adaptive capacity automatically adjusts partitions based on traffic patterns, mitigating hot keys. Option A (increase WCU) doesn't solve hot key issue. Option B (DAX) improves read, not write. Option D (remove sort key) would break the data model.

Answer

Enable DynamoDB Accelerator (DAX) to cache writes

Answer

Increase the provisioned write capacity units (WCU) to a higher value

Answer

Change the table design to use only partition key 'user_id' and remove the sort key

Question 2

A company is migrating an on-premises MongoDB workload to Amazon DocumentDB. The workload includes aggregation pipelines with $lookup and $group operations. The team wants to ensure minimal performance impact. Which THREE steps should they take?

Accepted Answer

Create appropriate indexes on fields used in $lookup and $group. Option A (enable TLS) is security, not performance. Option B (create indexes) is critical for $lookup and $group. Option C (increase instance size) helps compute-intensive operations. Option D (disable journaling) is not recommended for durability. Option E (use parallel scans) can speed up aggregations.

Answer

Disable journaling to reduce I/O overhead

Answer

Enable TLS for all connections

Question 3

A company is designing a global application that requires a database with multi-master writes across multiple AWS Regions with sub-second conflict resolution. Which AWS database service should they choose?

Accepted Answer

Amazon DynamoDB Global Tables. Amazon DynamoDB Global Tables provides multi-Region, multi-master replication with eventual consistency and sub-second conflict resolution. Option A (Aurora Global Database) has a single primary. Option C (RDS Multi-AZ) is single-Region. Option D (ElastiCache) is a cache.

Answer

Amazon ElastiCache for Redis Global Datastore

Answer

Amazon RDS with Multi-AZ

Answer

Amazon Aurora Global Database

Question 4

A company is migrating an on-premises MongoDB database to Amazon DocumentDB. The application uses secondary indexes extensively and requires low-latency reads. Which database design consideration is MOST important for this workload?

Accepted Answer

Convert secondary indexes to the DocumentDB-compatible format. Option B is correct because Amazon DocumentDB does not support the same range of secondary indexes as MongoDB; converting indexes ensures performance. Option A is wrong because DocumentDB uses its own storage, not EBS. Option C is wrong because DynamoDB Accelerator is for DynamoDB, not DocumentDB. Option D is wrong because vertical scaling is often insufficient; proper indexing is key.

Answer

Provision EBS-optimized instances with increased IOPS

Answer

Use a larger instance type to avoid indexing issues

Answer

Enable DynamoDB Accelerator (DAX) for caching

Question 5

Which THREE design patterns are appropriate for improving write performance in Amazon DynamoDB? (Choose 3.)

Accepted Answer

Partition data using a high-cardinality partition key. Options A, C, and D are correct: Using DynamoDB Accelerator (DAX) caches writes, partitioning data helps distribute write load, and using adaptive capacity handles uneven access patterns. Option B is wrong because global tables are for multi-region replication, not write performance. Option E is wrong because TTL is for automatic deletion, not write performance.

Answer

Enable DynamoDB global tables to distribute writes across regions

Answer

Implement TTL to automatically delete old items

Question 6

A company is migrating a 2 TB MySQL database to Amazon Aurora MySQL. They need to minimize downtime and ensure data consistency. Which approach should be used?

Accepted Answer

Use AWS DMS with ongoing replication (CDC).. Using AWS DMS with change data capture (CDC) from an on-premises source allows continuous replication, minimizing downtime. A full dump and restore requires downtime. SCT is for schema conversion. Direct connect alone doesn't handle migration.

Answer

Use mysqldump to export and import into Aurora.

Answer

Establish AWS Direct Connect and use MySQL replication.

Answer

Use AWS SCT to convert schema and data.

Question 7

A financial services company runs a core banking application on Amazon RDS for MySQL. They need to maintain a full audit trail of all changes to customer account balances for regulatory compliance. The audit trail must be immutable and queryable for up to 7 years. Which solution meets these requirements with minimal impact on the source database?

Accepted Answer

Migrate to Amazon Aurora MySQL and enable database activity streams, streaming to Amazon Kinesis Data Streams and then to Amazon S3. Amazon Aurora MySQL with database activity streams captures a near real-time feed of database activity and can be streamed to Amazon Kinesis Data Streams for analysis. This provides an immutable audit log. Option A uses binary logs which are not immutable and have limited retention. Option B is not immutable. Option D uses DynamoDB Streams but the source is RDS MySQL, not DynamoDB.

Answer

Use Amazon RDS Performance Insights to capture SQL queries and store them in Amazon S3

Answer

Use Amazon DynamoDB Streams with a Lambda function to capture changes from the MySQL database

Answer

Enable binary logging on the RDS instance and stream the binlog to Amazon S3 using AWS Database Migration Service (DMS)

Question 8

A company has a MySQL database that stores user profile data. The database is 1 TB and growing. The team wants to archive inactive user profiles that haven't been accessed in over 1 year. The archived data must be queryable but at a slower performance tier. Which approach is most cost-effective?

Accepted Answer

Export inactive profiles to Amazon S3 and use S3 Intelligent-Tiering for storage. Amazon S3 Intelligent-Tiering automatically moves data between access tiers to optimize costs. Querying S3 data can be done using Amazon Athena or S3 Select. Option A (RDS read replica) keeps all data in RDS, costly. Option B (DMS to S3) is a one-time load; S3 Intelligent-Tiering optimizes storage costs over time. Option D (DynamoDB TTL) deletes data, not archives.

Answer

Create an RDS read replica and delete inactive records from the primary

Answer

Move inactive profiles to Amazon Aurora Serverless and stop the cluster when not in use

Answer

Use Amazon DynamoDB with TTL to expire inactive profiles

Question 9

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 10

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.

Question 11

A company is designing a database for a global e-commerce platform with strong consistency requirements. The database must support cross-region disaster recovery with RPO < 1 second and RTO < 1 minute. Which TWO AWS database services meet these requirements?

Accepted Answer

Amazon Aurora Global Database. Option A (Aurora Global Database) provides cross-region replication with typical RPO of 1 second and RTO of 1 minute. Option D (DynamoDB Global Tables) offers multi-region replication with eventual consistency but also supports strongly consistent reads in each region; however, for global tables, RPO is typically < 1 second and failover can be automated within seconds. Option B (RDS Multi-AZ) is single-region. Option C (Redshift) is not designed for OLTP. Option E (ElastiCache) is in-memory and not durable.

Answer

Amazon RDS Multi-AZ

Answer

Amazon Redshift with cross-region snapshot copy

Answer

Amazon ElastiCache for Redis with Global Datastore

Question 12

A social media startup is selecting a database for user profiles with a flexible schema and high write throughput. The application is built on Node.js and requires low-latency access. Which database should they choose?

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is a NoSQL key-value and document database that offers flexible schema and high throughput with low latency. Option A (Aurora) is relational. Option B (RDS MySQL) is relational. Option D (ElastiCache) is a cache, not a primary database.

Answer

Amazon Aurora

Answer

Amazon ElastiCache for Redis

Answer

Amazon RDS for MySQL

Question 13

A startup is building a social media application that requires storing user profiles, posts, comments, and likes. The workload has variable traffic, with spikes after marketing campaigns. The team expects to run complex JOIN queries to generate a user's feed. Which AWS database service is MOST suitable for this relational workload?

Accepted Answer

Amazon RDS for PostgreSQL. Amazon RDS provides managed relational databases (MySQL, PostgreSQL) that support complex JOINs and can be scaled vertically or with read replicas. Option B is wrong because DynamoDB is NoSQL and does not natively support JOINs. Option C is wrong because ElastiCache is an in-memory cache, not a primary database. Option D is wrong because Neptune is a graph database, which is overkill and not optimized for typical relational queries.

Answer

Amazon Neptune

Answer

Amazon DynamoDB with global secondary indexes

Answer

Amazon ElastiCache for Redis

Question 14

Which THREE considerations are important when designing a database for a global, multi-Region application using Amazon DynamoDB Global Tables? (Select THREE.)

Accepted Answer

Application tolerance for eventually consistent reads. Global Tables replicate data across regions asynchronously, so conflict resolution (last writer wins) is important. Applications must handle eventually consistent reads. Write capacity must be provisioned in each region. Option D (strong consistency) is not guaranteed across regions. Option E (single write region) defeats the purpose of Global Tables.

Answer

Using a single write region to avoid conflicts

Answer

Strongly consistent reads across regions

Question 15

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