DBS-C01 Practice Test 22 — 15 Questions

Question 1

An e-commerce company is migrating its PostgreSQL database to Amazon RDS for PostgreSQL. The database has multiple large tables (over 500 GB each) and the migration window is only 2 hours. Which strategy would be MOST effective to meet the time constraint?

Accepted Answer

Use AWS DMS with parallel load by splitting tables into multiple tasks.. AWS DMS parallel load with multiple tasks allows concurrent data transfer, reducing total time. Increasing instance size alone may not be enough if the network is the bottleneck. SCT doesn't speed up data transfer. Homogeneous migration doesn't require SCT, but parallel load is more effective.

Answer

Use a single DMS task with full LOB mode.

Answer

Increase the RDS instance size and use pg_dump.

Answer

Use AWS SCT to optimize schema and then one DMS task.

Question 2

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 3

A financial services company needs a database for trade settlement records. Each trade must be processed exactly once and the database must ensure ACID compliance across multiple rows. The workload is write-intensive with moderate reads. Which AWS database service should they choose?

Accepted Answer

Amazon Aurora PostgreSQL. Option B is correct because Aurora is ACID-compliant, supports complex transactions, and provides high availability. Option A (DynamoDB) is not fully ACID (only single-item transactions are atomic). Option C (Neptune) is a graph database. Option D (ElastiCache) is not durable and not ACID.

Answer

Amazon DynamoDB with DynamoDB transactions

Answer

Amazon ElastiCache for Redis

Answer

Amazon Neptune

Question 4

Refer to the exhibit. A CloudFormation stack was deployed to create an RDS instance. The application team reports they cannot connect to the database using the endpoint provided. The security group allows inbound traffic on port 3306 from the application's security group. What is the most likely cause?

Accepted Answer

The database password is not provided in the stack outputs; the team may be using the wrong password. Option D is correct because the output shows the DBName and MasterUsername, but not the password. The password is usually stored in Secrets Manager or parameter store and not output. Option A: the endpoint appears correct. Option B: port 3306 is MySQL default, and the security group is allowed. Option C: Multi-AZ does not affect connectivity.

Answer

The RDS instance is in a Multi-AZ deployment and the endpoint is for the standby

Answer

The security group inbound rule is missing the port 3306

Answer

The RDS endpoint is incorrect; it should include the port number

Question 5

A company has an Amazon RDS for PostgreSQL instance that is running out of storage. The database is 2 TB in size and growing at 10 GB per day. They need a solution that allows automatic storage scaling with minimal downtime. What should they do?

Accepted Answer

Enable Storage Auto Scaling. Amazon RDS Storage Auto Scaling automatically increases storage when needed, with no downtime. Option A (manual snapshot) requires downtime. Option B (read replica) doesn't address storage. Option D (reserved instances) is a billing option.

Answer

Purchase reserved instances for cost savings

Answer

Create a read replica and promote it

Answer

Take a manual snapshot and restore to a larger instance

Question 6

A company runs a MySQL database on Amazon RDS for an e-commerce platform. The application performs frequent INSERT and UPDATE operations on the 'orders' table. The team notices an increase in disk I/O and CPU usage. They want to optimize the database for write-heavy workloads without changing the application. Which option is the MOST effective?

Accepted Answer

Increase the InnoDB buffer pool size. RDS provides enhanced monitoring and parameter groups. For write-heavy workloads, using InnoDB with appropriate buffer pool settings is key. Option A is wrong because switching to MyISAM is not recommended (no transaction support, table-level locking). Option B is wrong because enabling Multi-AZ does not improve write performance (synchronous replication adds latency). Option D is wrong because converting to Aurora MySQL would improve performance but is more expensive and not without changes.

Answer

Enable Multi-AZ deployment for redundancy

Answer

Change the storage engine to MyISAM

Answer

Upgrade to Amazon Aurora MySQL

Question 7

A company uses Amazon RDS for MySQL with Multi-AZ and read replicas. The database has a table storing user sessions with 50 million rows. The application team reports that queries using 'SELECT * FROM sessions WHERE user_id = ? ORDER BY login_time DESC LIMIT 10' are slow. The EXPLAIN plan shows a full table scan. Which design change would BEST improve query performance?

Accepted Answer

Create a composite index on (user_id, login_time). Option A is correct because a composite index on (user_id, login_time) allows the database to find rows by user and order by time without scanning. Option B is wrong because increasing instance size does not address the missing index. Option C is wrong because caching may help but does not fix the root cause. Option D is wrong because partitioning by user_id may help, but a composite index is more effective for this specific query.

Answer

Implement an application-level cache using ElastiCache

Answer

Partition the table by user_id

Answer

Upgrade to a larger instance type with more memory

Question 8

A company is investigating a performance issue with an Amazon Aurora MySQL database. The output of the describe-db-instances command is shown. The application experiences intermittent slowdowns during write-heavy periods. Which change would MOST likely improve write performance?

Accepted Answer

Add an Aurora Replica to distribute read traffic and reduce load on the writer. Option D is correct because Aurora's write performance is tied to cluster size; adding more nodes can distribute load. Option A is wrong because Aurora uses its own storage; changing to gp2 is not applicable. Option B is wrong because disabling encryption would compromise security and may not improve performance. Option C is wrong because Aurora MySQL does not have a provisioned IOPS setting like RDS.

Answer

Increase the provisioned IOPS to 10000

Answer

Change StorageType to gp2 and increase AllocatedStorage to 200 GB

Answer

Set StorageEncrypted to false to reduce encryption overhead

Question 9

A gaming company uses Amazon DynamoDB to store player profiles. Each profile is about 5 KB and is accessed frequently. The access pattern is mostly point reads by player ID. The company wants to reduce read costs while maintaining low latency. Currently, the table uses provisioned capacity with 3000 RCU. Which change would be MOST effective?

Accepted Answer

Use DynamoDB Accelerator (DAX) to cache frequently accessed items.. Option B is correct because DynamoDB Accelerator (DAX) caches reads, reducing RCU consumption. Option A is wrong because switching to on-demand may increase costs if traffic is steady. Option C is wrong because decreasing RCU would cause throttling. Option D is wrong because strongly consistent reads consume more RCU than eventually consistent.

Answer

Use strongly consistent reads instead of eventually consistent reads.

Answer

Switch from provisioned capacity to on-demand capacity mode.

Answer

Decrease the provisioned RCU to 2000 and rely on adaptive capacity.

Question 10

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 11

A company needs to store and query a graph of relationships between users for a recommendation engine. The queries involve traversing multiple edges. Which AWS database service is most suitable?

Accepted Answer

Amazon Neptune. Option B is correct because Neptune is a fully managed graph database designed for highly connected data. Option A (RDS) requires complex joins. Option C (DynamoDB) can model graphs but requires multiple queries. Option D (DocumentDB) is for documents.

Answer

Amazon DynamoDB with adjacency list design

Answer

Amazon DocumentDB (with MongoDB compatibility)

Answer

Amazon RDS for PostgreSQL with recursive CTEs

Question 12

A company runs a critical PostgreSQL database on Amazon RDS and needs to implement point-in-time recovery (PITR) with a recovery window of the last 35 days. Currently, automated backups are set to retain for 35 days. The database size is 500 GB. What additional configuration is required?

Accepted Answer

No additional configuration is required; automated backups enable PITR. Automated backups in RDS by default support PITR within the retention period. No additional configuration is needed. Option A (manual snapshots) is not required. Option B (Multi-AZ) doesn't affect PITR. Option D (log shipping) is not a separate feature.

Answer

Enable manual snapshots every hour

Answer

Set up a replication slot and stream transaction logs to S3

Answer

Enable Multi-AZ deployment

Question 13

A financial services company runs a critical PostgreSQL database on Amazon RDS. The database stores transaction records and requires point-in-time recovery (PITR) with a recovery window of 35 days. The database size is 500 GB and grows at 10 GB per day. The team wants to minimize storage costs while meeting the recovery SLA. Which backup strategy should they use?

Accepted Answer

Enable automated backups with a retention period of 35 days. Amazon RDS automated backups provide PITR within the retention period (up to 35 days). They store transaction logs continuously, allowing recovery to any second within the window. Option B is wrong because manual snapshots every hour would be expensive and cumbersome. Option C is wrong because cross-region snapshots do not provide PITR and are for disaster recovery. Option D is wrong because disabling automated backups and using pg_dump would lose ability to recover to a specific point in time.

Answer

Take manual snapshots every hour and retain for 35 days

Answer

Disable automated backups and use pg_dump to S3 daily

Answer

Use AWS Backup to copy snapshots to another region daily

Question 14

A company is designing a database for a global application that requires low-latency reads and writes across multiple AWS regions. The application data is key-value and does not require complex queries. The team needs strong consistency for critical data. Which TWO services should they consider? (Choose TWO.)

Accepted Answer

Amazon DynamoDB Global Tables. DynamoDB Global Tables provide multi-region replication with strong consistency option. Option A is wrong because RDS cross-region read replicas do not support writes in multiple regions. Option D is wrong because S3 is not a database for key-value low-latency. Option E is wrong because ElastiCache is a cache, not a durable database.

Answer

Amazon S3 with cross-region replication

Answer

Amazon ElastiCache for Redis with global datastore

Answer

Amazon RDS for PostgreSQL with cross-region read replicas

Question 15

Which TWO of the following are advantages of using Amazon DynamoDB over Amazon RDS for MySQL for a workload that requires high scalability and low maintenance? (Select TWO.)

Accepted Answer

No need to manage database servers or patches. DynamoDB automatically scales throughput and storage, and it is fully managed with no server administration. Option C is true for RDS, not DynamoDB. Option D is false because DynamoDB supports both consistency models. Option E is true for RDS, not DynamoDB.

Answer

Strong consistency by default

Answer

Support for complex joins and transactions

Answer

Built-in read replicas for scaling reads