DBS-C01 Practice Exam 51 — 20 Questions

Question 1

A company is migrating a 2 TB PostgreSQL database from on-premises to Amazon RDS for PostgreSQL. The database has a 4-hour downtime window. The company requires minimal data loss and wants to use AWS DMS. The on-premises network has a 100 Mbps internet connection. Which migration method should the company use?

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

Accepted Answer

Use AWS DMS with a full load and ongoing change data capture (CDC) replication.. AWS DMS with a full load and ongoing change data capture (CDC) replication allows the company to migrate the 2 TB database with minimal data loss within the 4-hour downtime window. The full load transfers the existing data, and CDC captures and applies ongoing changes from the source database to the target RDS instance, reducing the final cutover downtime to seconds or minutes. This approach is ideal for large databases with tight downtime constraints and limited bandwidth (100 Mbps), as the initial full load can run before the downtime window, and only the final CDC catch-up occurs during the window.

Answer

Use AWS Schema Conversion Tool (SCT) to migrate the data to Amazon RDS.

Answer

Use AWS DMS with a full load only, then stop the source database and resume applications.

Answer

Use pg_dump and pg_restore to export and import the database during the downtime window.

Question 2

A company uses Amazon RDS for PostgreSQL and needs to ensure that only specific IP addresses can connect to the database. Which configuration should be used?

Accepted Answer

Modify the VPC security group associated with the DB instance to allow inbound traffic only from specific IP addresses.. A VPC security group acts as a virtual firewall for the RDS instance and controls inbound traffic at the network layer, so modifying its inbound rules to allow only specific CIDR ranges is the correct way to restrict which IP addresses can connect. RDS instances reside in a VPC subnet and are governed by the security group attached to them. This is the standard, supported method for IP-based access control to RDS.

Answer

Configure the DB subnet group to allow only specific IP addresses.

Answer

Set the rds.force_ssl parameter in the DB parameter group.

Answer

Create an IAM policy that restricts access to the RDS API based on source IP.

Question 3

A company is running an Amazon RDS for MySQL DB instance. The database performance has degraded over time, and the company suspects that slow queries are the cause. Which AWS service should the company use to identify the slow queries and analyze the database performance?

Accepted Answer

Amazon RDS Performance Insights. Amazon RDS Performance Insights is designed to identify slow queries and analyze database performance by visualizing database load and wait events. It provides a top SQL view that shows which queries are consuming the most resources, making it the right tool for diagnosing slow queries. It integrates directly with RDS for MySQL and requires no additional setup beyond enabling it.

Answer

AWS Trusted Advisor

Answer

Amazon RDS Enhanced Monitoring

Answer

Amazon CloudWatch Logs

Question 4

A company is using Amazon DynamoDB with global tables (multi-region) for a gaming application. The application writes to a table in us-east-1 and reads from a table in eu-west-1. The team notices that writes in us-east-1 are taking longer than expected to propagate to eu-west-1. What is the most likely cause?

Accepted Answer

Network latency between the regions is causing replication delay. DynamoDB global tables replicate writes asynchronously across regions, and the replication latency is dominated by the physical network round-trip time between regions. us-east-1 to eu-west-1 is a transatlantic path, so propagation typically takes on the order of a second or more, which is expected behavior rather than a fault. The other options describe conditions that would not cause replication delay.

Answer

The write capacity in eu-west-1 is insufficient

Answer

Conflicts are being resolved due to concurrent writes

Answer

DynamoDB Streams is disabled on the table

Question 5

A financial services company runs a critical application on Amazon RDS for MySQL. The database stores transaction data that must be retained for 7 years for regulatory compliance. The current retention policy stores all data in the same table, causing performance degradation on the main transactional table. The company needs to archive data older than 1 year while keeping it queryable. Which design should they implement?

Accepted Answer

Use Amazon RDS for MySQL with a read replica for reporting, and set up a Lambda function to export partitions older than 1 year to Amazon S3 in Parquet format, queryable via Amazon Athena.. It uses RDS for MySQL read replicas to offload reporting traffic, while a Lambda function archives partitions older than 1 year to Amazon S3 in Parquet format. This keeps the main transactional table lean, improves performance, and retains data for 7 years in a cost-effective, queryable format via Amazon Athena, meeting both compliance and queryability requirements.

Answer

Migrate to Amazon Redshift and use workload management to prioritize transactions.

Answer

Use Amazon ElastiCache for Redis to cache recent data and move old data to S3.

Answer

Migrate to Amazon DynamoDB with TTL to automatically expire old data.

Question 6

A company wants to migrate an on-premises MySQL database to Amazon RDS for MySQL with minimal downtime. The database is 500 GB and has moderate write activity. Which approach is MOST suitable?

Accepted Answer

Use AWS Database Migration Service (DMS) with a full load and ongoing replication.. AWS DMS with full load and ongoing replication is the most suitable approach because it supports continuous change data capture (CDC) from the on-premises MySQL source to the Amazon RDS target, enabling minimal downtime. The full load transfers the initial 500 GB dataset, while ongoing replication applies incremental changes until cutover, meeting the requirement for minimal downtime with moderate write activity.

Answer

Use mysqldump to export the database, then import into RDS.

Answer

Use AWS Server Migration Service (SMS) to migrate the database server.

Answer

Create a read replica of the on-premises database and promote it to RDS.

Question 7

A company is running an Amazon RDS for SQL Server DB instance. The company needs to capture changes to a specific table and replicate them to an Amazon S3 bucket in near real time. Which AWS service should be used to achieve this?

Accepted Answer

AWS Database Migration Service (AWS DMS) with ongoing replication. AWS DMS with ongoing replication (change data capture) is the correct choice because it can continuously capture changes from the RDS for SQL Server source and replicate them to an Amazon S3 bucket in near real time. Option A (AWS Glue) is incorrect because AWS Glue is a batch ETL service, not designed for real-time change data capture. Option C (Amazon RDS for SQL Server native replication) is incorrect because native replication features like Always On Availability Groups or log shipping replicate data to another SQL Server instance, not directly to S3. Option D (Amazon Kinesis Data Streams) is incorrect because while it can ingest streaming data, it would require additional custom application logic to capture changes from RDS and push to Kinesis, making it less straightforward than DMS for this use case.

Answer

AWS Glue

Answer

Amazon RDS for SQL Server native replication

Answer

Amazon Kinesis Data Streams

Question 8

A company is using Amazon Redshift for data warehousing. They notice that query performance has degraded over time. The database administrator checks the system tables and finds that there is significant skew in data distribution across slices. What action should be taken to improve query performance?

Accepted Answer

Recreate the table with a different distribution style, such as KEY distribution on a column with high cardinality.. Data skew in Amazon Redshift means that data is unevenly distributed across slices, causing some slices to work harder than others during query execution, leading to performance degradation. Recreating the table with a different distribution style, such as KEY distribution on a high-cardinality column, can evenly distribute data and improve parallel processing. This directly addresses the root cause of skew.

Answer

Increase the number of nodes in the cluster.

Answer

Run the VACUUM command to reclaim space and update statistics.

Answer

Modify the sort keys to better match the query patterns.

Question 9

A company uses Amazon ElastiCache for Redis. They want to monitor cache hit ratio. Which TWO metrics should be used to calculate the cache hit ratio?

Accepted Answer

CacheHits. Cache hit ratio is calculated as CacheHits divided by (CacheHits + CacheMisses), so option B (CacheHits) and option D (CacheMisses) are the two metrics needed. CacheHits counts the number of successful read-only key lookups in the main dictionary, while CacheMisses counts the number of unsuccessful read-only key lookups, and together they represent the total number of read attempts. Option A (GetTypeCmds) counts the total number of read-only type commands and does not distinguish hits from misses, so it cannot be used to compute the ratio. Option C (Evictions) tracks keys evicted due to maxmemory limits, which relates to memory pressure rather than hit/miss performance. Option E (CurItems) reports the current number of items stored in the cache, which is a capacity metric, not a hit/miss metric.

Answer

GetTypeCmds

Answer

Evictions

Answer

CurItems

Question 10

A company runs an Amazon RDS for MySQL Multi-AZ DB instance. The application experiences intermittent read latency spikes. The DB instance type is db.r5.large with 500 GB of General Purpose SSD (gp2) storage. The spike occurs during peak hours when read activity is high. Which action would most effectively reduce read latency?

Accepted Answer

Create an Amazon RDS read replica and direct read traffic to it.. A read replica is a separate DB instance that receives asynchronous replication from the primary, so it offloads read traffic from the primary instance entirely. This directly addresses read latency caused by contention on the primary during peak read activity. Multi-AZ standby cannot serve reads (it exists only for failover), and storage changes don't help when the bottleneck is instance-level read throughput.

Answer

Change the storage type to Provisioned IOPS (io1).

Answer

Enable Multi-AZ with a standby replica.

Answer

Increase the allocated storage to 1 TB to improve IOPS.

Question 11

A database administrator notices that an Amazon RDS for MySQL DB instance is experiencing high CPU utilization and increased latency during peak hours. The administrator wants to identify the queries causing the issue. Which TWO actions should be taken to diagnose the problem? (Select TWO.)

Accepted Answer

Enable Performance Insights on the DB instance.. Enabling Performance Insights provides database performance metrics including wait events and SQL query details, allowing identification of queries causing high CPU and latency. Option C: Enabling the slow query log captures queries that exceed a specified duration threshold, helping to pinpoint slow-running queries. Option B (Amazon DevOps Guru for RDS) is an automated service for anomaly detection and performance insights, not a direct method to identify specific queries. Option D (RDS Proxy) manages connection pooling and improves scalability, but does not identify problematic queries. Option E (RDS Enhanced Monitoring) provides OS-level metrics, not query-level details.

Answer

Enable Amazon DevOps Guru for RDS.

Answer

Use RDS Proxy to manage connections.

Answer

Enable RDS Enhanced Monitoring.

Question 12

A company is migrating a 500 GB on-premises PostgreSQL database to Amazon RDS for PostgreSQL. The migration must have minimal downtime and support ongoing replication after the initial load. Which AWS service should be used?

Accepted Answer

AWS Database Migration Service (DMS) with ongoing replication. AWS Database Migration Service (DMS) with ongoing replication (change data capture, CDC) is required because the scenario demands minimal downtime and continuous synchronization after the initial 500 GB load. DMS uses transaction logs (e.g., PostgreSQL WAL) to capture and apply ongoing changes, enabling a near-zero-duration cutover. Full load only (Option B) would cause downtime during the final sync and cannot support ongoing replication.

Answer

AWS Schema Conversion Tool (SCT)

Answer

AWS Database Migration Service (DMS) with full load only

Answer

AWS Glue

Question 13

A company runs a web application on Amazon EC2 instances behind an Application Load Balancer. The application uses Amazon RDS for MySQL. Recently, the database CPU utilization spikes to 100% during peak hours. The team observes that the spike is caused by a large number of slow queries. They need to identify and resolve the issue with minimal disruption. Which combination of steps should they take? (Choose two.)

Accepted Answer

Enable RDS Performance Insights to identify the slow queries. Option A is correct because RDS Performance Insights provides detailed database load analysis, showing top SQL statements, wait events, and hosts, which lets the team pinpoint exactly which slow queries are driving CPU to 100% during peak hours. Option D is correct because offloading reporting or read-heavy queries to a read replica removes that workload from the primary DB instance, directly reducing CPU utilization on the primary while keeping the application available with minimal disruption. Option B is not appropriate because simply scaling up the instance type masks the symptom rather than identifying the slow queries, and it causes a disruptive failover/reboot. Option C is wrong because increasing storage/IOPS addresses I/O bottlenecks, not CPU consumed by slow queries. Option E is wrong because RDS Proxy improves connection management and failover, but it does not identify slow queries nor reduce CPU caused by inefficient SQL.

Answer

Upgrade to a larger instance type

Answer

Increase the DB instance storage to improve I/O

Answer

Implement connection pooling using Amazon RDS Proxy

Question 14

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 for PostgreSQL is the most suitable choice because the workload requires complex JOIN queries on relational data (user profiles, posts, comments, likes). PostgreSQL provides full SQL support, ACID compliance, and robust indexing capabilities (e.g., B-tree, GiST, GIN) that efficiently handle multi-table joins. RDS also offers managed scaling, automated backups, and read replicas to accommodate traffic spikes after marketing campaigns.

Answer

Amazon Neptune

Answer

Amazon DynamoDB with global secondary indexes

Answer

Amazon ElastiCache for Redis

Question 15

A company is designing a security architecture for Amazon DynamoDB. They need to ensure that only authorized applications can access the data, and that data in transit is encrypted. Which THREE steps should be taken? (Choose THREE.)

Accepted Answer

Attach an IAM policy that grants access only to specific IAM roles or users.. Option B is correct because IAM policies are the primary authorization mechanism for DynamoDB, allowing you to grant least-privilege access to specific IAM roles or users via actions like dynamodb:GetItem and dynamodb:PutItem on specific table ARNs. Option C is correct because an AWS PrivateLink VPC endpoint (interface endpoint) lets applications reach DynamoDB over the AWS private network instead of the public internet, keeping traffic off the public internet and enabling endpoint policies and security-group control on the endpoint ENIs. Option E is correct because DynamoDB encrypts data in transit by requiring HTTPS/TLS for all API calls to endpoints like dynamodb.us-east-1.amazonaws.com, protecting data in transit. Option A is incorrect because KMS keys encrypt data at rest, not data in transit. Option D is incorrect because DynamoDB is a managed service without security groups on the table itself; security groups apply to the VPC endpoint ENIs, not to the DynamoDB table.

Answer

Use a customer-managed KMS key to encrypt data in transit.

Answer

Configure a security group to restrict inbound traffic to the DynamoDB table.

Question 16

A company is migrating a 5 TB MySQL database to Amazon RDS for MySQL. They need to minimize downtime. Which approach should they use?

Accepted Answer

Use AWS DMS with full load and change data capture (CDC). AWS DMS with full load and change data capture (CDC) minimizes downtime by performing an initial full load of the 5 TB database while continuously replicating ongoing changes from the source. Once the full load completes and the target is nearly synchronized, you can cut over with minimal downtime, typically seconds to minutes. This approach is specifically designed for large-scale migrations with low downtime requirements.

Answer

Use Percona XtraBackup to take a backup and restore to RDS

Answer

Use mysqldump to export and import data

Answer

Use AWS DataSync to copy database files

Question 17

Refer to the exhibit. An application team notices that the MySQL RDS instance 'mydb' is running at 80% CPU utilization during peak hours. They need to improve read performance without increasing the CPU load on the primary instance. Which action should they take?

Accepted Answer

Create a Read Replica in the same region. Creating a Read Replica offloads read traffic from the primary MySQL RDS instance, reducing CPU load on the primary while improving read performance for applications. Read Replicas asynchronously replicate data using MySQL’s native binlog-based replication, allowing the primary to focus on write operations without additional CPU overhead from serving reads.

Answer

Increase the DB instance class to db.r5.xlarge

Answer

Change storage type to io1 with higher IOPS

Answer

Enable Multi-AZ deployment

Question 18

A company is running a MySQL database on an EC2 instance and wants to migrate to Amazon RDS for MySQL with minimal downtime. The database is 500 GB in size and has a high write workload. Which migration approach is most appropriate?

Accepted Answer

Use AWS Database Migration Service (DMS) with ongoing replication.. AWS DMS with ongoing replication (change data capture) is the most appropriate approach because it allows you to migrate the 500 GB database with minimal downtime. DMS performs a full load of the existing data and then continuously replicates ongoing changes from the source MySQL EC2 instance to the target Amazon RDS for MySQL, enabling a cutover with only a brief pause in writes.

Answer

Export data to Amazon S3 and use AWS Glue to load into RDS.

Answer

Copy the MySQL data directory to Amazon EBS and attach to RDS.

Answer

Take a mysqldump from the source and import into RDS.

Question 19

A company is using Amazon DynamoDB with server-side encryption enabled. They need to ensure that all access to the table is audited. Which service should be used to capture data-plane API calls?

Accepted Answer

AWS CloudTrail. AWS CloudTrail, when configured to capture data events, can record DynamoDB data-plane API calls such as GetItem and PutItem. Option A (VPC Flow Logs) captures network traffic, not API calls. Option B (AWS Config) records configuration changes, not data-plane actions. Option C (Amazon CloudWatch Logs) can store logs but does not directly capture API calls; it would require another service to send logs to it.

Answer

VPC Flow Logs

Answer

AWS Config

Answer

Amazon CloudWatch Logs

Question 20

A company runs an Amazon RDS for SQL Server database. The database size is 500 GB. The company needs to create a test environment with a copy of the production database that refreshes daily. Which THREE steps should be taken to automate this? (Choose THREE.)

Accepted Answer

Use AWS Backup or AWS Lambda to take a manual snapshot of the production DB instance daily.. Creates a manual snapshot of the production DB instance daily using AWS Backup or Lambda. Option D restores that snapshot to a new DB instance in the test environment. Option B updates the test application's connection string to point to the new test instance. Option C is incorrect because a read replica is not a full copy and promoting it would disrupt replication, not provide a daily refreshed copy. Option E is unnecessary because the restored instance can have automated backups enabled, but it is not a required step for the daily refresh process.

Answer

Create a read replica of the production instance and promote it to the test environment.

Answer

Enable automated backups on the test instance after restoration.