DBS-C01 Practice Questions 1 — 50 Questions

Question 1

A database administrator wants to receive an alert when an RDS instance's storage space drops below 10% of total allocated storage. Which AWS service should be used to set up this alert?

Accepted Answer

Amazon CloudWatch Alarms. Amazon CloudWatch Alarms is the correct service because it evaluates CloudWatch metrics against thresholds and triggers actions such as SNS notifications. For RDS, the FreeStorageSpace metric can be compared to a percentage of allocated storage using a metric math expression, and an alarm can fire when it drops below 10%. CloudWatch is the native monitoring and alerting layer for RDS.

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Amazon SNS

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AWS CloudTrail

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AWS Config

Question 2

A database specialist notices that an RDS MySQL instance's FreeableMemory metric is consistently below 100 MB. Which monitoring tool should be used to identify the queries consuming the most memory?

Accepted Answer

Performance Insights. Performance Insights is the correct tool because it provides detailed monitoring of database load and allows you to identify the queries consuming the most memory. It visualizes database load by wait events and top SQL, helping pinpoint memory-intensive queries. FreeableMemory is an OS-level metric, but Performance Insights drills down to the SQL level.

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Amazon S3 access logs

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AWS CloudTrail

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CloudWatch Logs

Question 3

A company is migrating its on-premises Oracle database to Amazon RDS for Oracle. The database specialist needs to monitor the migration process and ensure data consistency. Which TWO AWS services should be used together to continuously monitor the replication lag and data integrity?

Accepted Answer

AWS Database Migration Service (AWS DMS). AWS DMS is the correct service because it is specifically designed for database migrations and provides built-in monitoring of replication lag via the 'CDC latency' metric. Amazon CloudWatch is the correct complementary service because it collects and visualizes DMS metrics, including replication lag and task status, and can trigger alarms if data integrity or latency thresholds are breached.

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Amazon RDS Performance Insights

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AWS Schema Conversion Tool (AWS SCT)

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AWS Glue

Question 4

A company is migrating a PostgreSQL database to Amazon Aurora PostgreSQL. They have set up AWS DMS with change data capture (CDC). However, after the initial load, the CDC replication is experiencing high latency. What is the MOST likely cause?

Accepted Answer

The source database has large transactions that are not committed quickly.. Large uncommitted transactions on the source database cause DMS CDC to buffer changes until the transaction commits, leading to high latency. DMS must wait for the commit record before applying changes to the target Aurora instance, and during this time, CDC replication stalls, accumulating a backlog of changes.

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The target Aurora instance has insufficient storage.

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The DMS instance is using an older engine version.

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The network bandwidth is too low.

Question 5

A database specialist needs to monitor the performance of an Amazon Aurora PostgreSQL cluster and identify the top SQL statements by total time. Which AWS tool provides this information with minimal setup?

Accepted Answer

AWS Performance Insights with the Aurora PostgreSQL cluster.. AWS Performance Insights provides a user-friendly dashboard that shows top SQL statements by database load, including total time. It requires only enabling the feature on the Aurora cluster, with no additional agents or configuration. Other options either provide OS metrics, require log parsing, or are for auditing, not performance analysis.

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Amazon CloudWatch Logs Insights with Aurora PostgreSQL error logs.

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AWS CloudTrail with database activity streams.

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Amazon RDS Enhanced Monitoring with OS metrics.

Question 6

A company is using an Amazon RDS for MySQL DB instance. The security team requires that all database connections be encrypted in transit. Which configuration step ensures this requirement is met?

Accepted Answer

Set the 'require_secure_transport' parameter to 1 in the DB parameter group.. For Amazon RDS for MySQL, encryption in transit is enforced by setting the require_secure_transport parameter to 1 in the DB parameter group. This forces all client connections to use SSL/TLS, rejecting any unencrypted connection attempts. The parameter is dynamic and can be applied without a reboot in most cases.

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Enable encryption at rest for the RDS instance.

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Store the database password in AWS Secrets Manager.

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Modify the network ACL to only allow traffic on port 3306.

Question 7

A database team is migrating an on-premises Oracle database to Amazon Aurora PostgreSQL. The team needs to ensure minimal downtime and data consistency. Which approach should be used?

Accepted Answer

Use AWS Database Migration Service (DMS) with ongoing replication using change data capture (CDC). AWS DMS with ongoing replication using change data capture (CDC) is the correct approach because it enables a live migration with minimal downtime. DMS can perform a full load of the Oracle database and then continuously replicate ongoing changes from Oracle to Aurora PostgreSQL, ensuring data consistency at the point of cutover. This method avoids the need for a long maintenance window and supports heterogeneous migrations with automatic schema conversion.

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Use the PostgreSQL foreign data wrapper (FDW) to link the Oracle database

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Use AWS Server Migration Service (SMS) to replicate the database

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Use pg_dump and pg_restore to migrate the data during a maintenance window

Question 8

A company stores sensitive data in an Amazon S3 bucket that is accessed by an Amazon Redshift cluster. The security team requires that the data in transit between Redshift and S3 be encrypted. Which configuration ensures this?

Accepted Answer

Ensure that the Redshift cluster has SSL enabled, which encrypts data in transit by default for COPY/UNLOAD operations to S3.. Redshift automatically uses SSL encryption for data in transit when moving data to and from S3 using COPY/UNLOAD commands. Option A is incorrect because server-side encryption (SSE-S3) encrypts data at rest, not in transit. Option C is incorrect because client-side encryption encrypts data before sending, but Redshift handles this automatically with SSL. Option D is incorrect because VPC endpoints do not encrypt data in transit; they provide private connectivity.

Answer

Enable server-side encryption (SSE-S3) on the S3 bucket.

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Configure a VPC endpoint for S3.

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Use client-side encryption on the data before uploading to S3.

Question 9

Which TWO of the following are recommended best practices for designing a relational database on Amazon RDS? (Select TWO.)

Accepted Answer

Use read replicas to scale read-heavy workloads. Amazon RDS read replicas offload read traffic from the primary DB instance, improving performance for read-heavy workloads by providing additional read-only endpoints. This is a core best practice for scaling read capacity without increasing load on the source instance.

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Use LOB data types to store large text fields

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Use non-EBS-optimized instances to reduce costs

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Store large binary objects (BLOBs) in the database

Question 10

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database size is 500 GB. The migration must have minimal downtime. Which AWS service should be used to perform the migration?

Accepted Answer

AWS Database Migration Service (DMS). AWS Database Migration Service (DMS) is the correct choice because it supports heterogeneous migrations from Oracle to Amazon RDS for Oracle with minimal downtime. DMS can perform continuous replication using Oracle's change data capture (CDC) via LogMiner or binary reader, allowing the source database to remain operational during the migration. This makes it ideal for a 500 GB database where downtime must be minimized.

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AWS Snowball Edge

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AWS DataSync

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Amazon RDS for Oracle snapshot copy

Question 11

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 the correct choice because it is a fully managed NoSQL key-value and document database that offers flexible schema (schemaless), single-digit millisecond latency at any scale, and is designed for high write throughput. It integrates natively with Node.js via the AWS SDK and supports auto-scaling to handle unpredictable write loads, making it ideal for a social media startup's user profile store.

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Amazon Aurora

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Amazon ElastiCache for Redis

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Amazon RDS for MySQL

Question 12

A company needs to store and query time-series data from IoT devices. The data arrives in high volume and requires efficient range queries over time. Which database is most appropriate?

Accepted Answer

Amazon Timestream. Amazon Timestream is a purpose-built time-series database that automatically scales to handle high-volume IoT data and is optimized for efficient range queries over time. It separates storage into a memory store for recent data and a magnetic store for historical data, enabling fast queries across time ranges with built-in time-series functions.

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Amazon RDS for MySQL

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Amazon DynamoDB

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Amazon Redshift

Question 13

A company is designing a database for a mobile application that requires offline synchronization. Users should be able to read and write data while offline, and changes should sync when connectivity is restored. Which AWS service supports this pattern?

Accepted Answer

AWS AppSync with Amazon DynamoDB. AWS AppSync with Amazon DynamoDB is correct because AppSync provides managed GraphQL APIs that support offline data synchronization via its client SDKs. When a mobile app is offline, mutations are queued locally and automatically replayed against DynamoDB once connectivity is restored, using a conflict resolution mechanism (e.g., last-writer-wins or custom resolvers) to merge changes.

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Amazon RDS Proxy

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Amazon S3 Transfer Acceleration

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Amazon Cognito

Question 14

A security engineer is designing a VPC with an RDS instance. The database must not be accessible from the internet, but EC2 instances in a private subnet must connect. Which security group configuration is MOST secure?

Accepted Answer

Set the RDS security group inbound rule to allow traffic from the EC2 security group on port 3306.. The most secure because it uses a security group reference instead of a CIDR block. By referencing the EC2 security group as the source in the RDS security group inbound rule, only instances associated with that specific security group can communicate with the database on port 3306. This approach adheres to the principle of least privilege and automatically scales as instances are added or removed from the EC2 security group, without needing to update CIDR ranges.

Answer

Set the RDS security group inbound rule to allow traffic from the VPC CIDR on port 3306.

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Set the RDS security group inbound rule to allow traffic from 0.0.0.0/0 on port 3306.

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Set the RDS security group inbound rule to allow traffic from the private subnet CIDR on port 3306.

Question 15

A company is running a critical application on Amazon RDS for Oracle. They need to ensure high availability with automatic failover in case of a database failure. The database size is 500 GB. Which solution should they implement?

Accepted Answer

Enable Multi-AZ deployment. Multi-AZ deployment for Amazon RDS for Oracle provides synchronous replication to a standby instance in a different Availability Zone, with automatic failover in the event of a database failure. This ensures high availability without manual intervention, meeting the requirement for automatic failover for a 500 GB Oracle database.

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Create a cross-Region read replica

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Migrate to Amazon DynamoDB Global Tables

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Take regular snapshots and restore in a different Availability Zone

Question 16

A company is using Amazon DynamoDB with on-demand capacity. The application experiences increased latency during peak hours. The DynamoDB table receives about 5,000 writes per second and 10,000 reads per second. The read latency is high, but write latency is acceptable. What should the company do to reduce read latency?

Accepted Answer

Enable DynamoDB Accelerator (DAX) for the table.. DynamoDB Accelerator (DAX) is a fully managed, highly available, in-memory cache that significantly reduces read latency for DynamoDB tables, especially for repeated reads. DAX allows you to offload read traffic from the table and serve read requests from the cache, reducing the load on the table and improving response times. Option A is wrong because DynamoDB Streams is used to capture changes to items in the table, not to cache data or offload read traffic. Option B is wrong because DynamoDB does not support read replicas; DAX is the caching solution for reads. Option D is wrong because switching to provisioned capacity and enabling auto scaling would help with scaling write capacity but does not directly address high read latency; DAX is specifically designed for in-memory caching to improve read performance.

Answer

Enable DynamoDB Streams to offload read traffic.

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Create a read replica of the DynamoDB table.

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Switch to provisioned capacity and enable auto scaling.

Question 17

A financial services company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database has a high volume of write transactions and requires minimal downtime during migration. Which AWS service or feature should be used to replicate data continuously to the target RDS instance during the migration?

Accepted Answer

AWS Database Migration Service (AWS DMS) with ongoing replication. AWS Database Migration Service (AWS DMS) with ongoing replication (change data capture, CDC) is the correct choice because it continuously captures and applies changes from the source Oracle database to the target Amazon RDS for Oracle instance, enabling near-zero downtime during migration. This is achieved by using Oracle's redo logs to stream transactions in real time, which meets the high write volume and minimal downtime requirements.

Answer

Amazon RDS Read Replica

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Amazon RDS Multi-AZ deployment

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AWS Schema Conversion Tool (AWS SCT)

Question 18

A company is designing a database for an e-commerce platform that requires high availability and automatic failover with minimal downtime. The application performs both OLTP and read-heavy analytics. Which AWS database service should be used?

Accepted Answer

Amazon Aurora. Amazon Aurora is the correct choice because it combines the high availability and automatic failover of a relational database with the performance needed for both OLTP and read-heavy analytics. Aurora provides six-way replication across three Availability Zones, automatic failover in under 30 seconds, and supports up to 15 low-latency read replicas that can offload analytics queries without impacting write performance.

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Amazon DynamoDB

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Amazon RDS for MySQL

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Amazon Redshift

Question 19

A startup is building a social media application that needs to store user profiles, posts, comments, and likes. The data is highly interconnected, and the team wants to query relationships efficiently, such as 'find all friends of a user who liked a post'. Which database service is best suited for this workload?

Accepted Answer

Amazon Neptune. Amazon Neptune is a fully managed graph database service optimized for highly interconnected data. It supports property graph and RDF models, enabling efficient traversal of relationships such as 'find all friends of a user who liked a post' using Gremlin or SPARQL queries. This makes it the ideal choice for social media applications requiring real-time relationship queries.

Answer

Amazon ElastiCache for Redis

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Amazon DynamoDB

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Amazon RDS for PostgreSQL

Question 20

A database administrator is troubleshooting an Amazon RDS for PostgreSQL DB instance that is experiencing high CPU utilization. The administrator runs the following query to find the current running queries:

SELECT pid, now() - pg_stat_activity.query_start AS duration, query, state
FROM pg_stat_activity
WHERE state = 'active';

The output shows a high number of queries with a state of 'active' and durations exceeding several minutes. What should the administrator do FIRST to reduce CPU utilization?

Accepted Answer

Use pg_terminate_backend to terminate the long-running queries.. The immediate cause of high CPU utilization is the long-running active queries consuming resources. Using pg_terminate_backend to terminate these queries will quickly free up CPU cycles, providing immediate relief. This is the first troubleshooting step before making configuration changes or scaling, as it directly addresses the symptom shown in the pg_stat_activity output.

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Modify the max_connections parameter to limit concurrent sessions.

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Scale up the DB instance to a larger instance class.

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Enable pg_stat_statements to collect query performance data.