DBS-C01 Practice Test 29 — 15 Questions

Question 1

Which TWO of the following are benefits of using Amazon DynamoDB Accelerator (DAX)? (Choose 2.)

Accepted Answer

Reduces read latency to microseconds for cached items. Amazon DynamoDB Accelerator (DAX) is an in-memory cache that delivers up to 10x read performance improvement, reducing read latency to microseconds for cached items. It sits between your application and DynamoDB, intercepting read requests and serving them from its cluster's memory, which avoids the millisecond-level latency of reading from DynamoDB's SSD storage.

Answer

Improves write throughput by caching write operations

Answer

Reduces storage costs by compressing data

Answer

Automatically scales write capacity based on demand

Question 2

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 with parallel load by splitting tables into multiple tasks allows concurrent data transfer across multiple threads, maximizing throughput for large tables. This approach directly addresses the 2-hour migration window by distributing the workload, whereas a single task would be bottlenecked by sequential processing. Parallel load is specifically designed for high-volume migrations where time is critical.

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 3

A company uses Amazon Redshift and notices that queries are taking longer than usual. CloudWatch metrics show 'CPUUtilization' is high and 'DiskSpace' is low. Which TWO actions can help improve query performance?

Accepted Answer

Add more nodes to the cluster. Adding nodes increases both compute capacity and storage, addressing high CPU and low disk space. Option E is correct because optimizing sort keys reduces the amount of data scanned per query, which lowers CPU usage and speeds up queries. Option A is incorrect because disabling concurrency scaling would reduce the cluster's ability to handle concurrent queries, increasing wait times. Option C is incorrect because Multi-AZ is not a feature of Amazon Redshift; it's used for RDS. Option D is incorrect because VACUUM reorganizes data but requires free disk space to operate; with low disk space, it may fail or not help.

Answer

Disable concurrency scaling to free resources

Answer

Enable Multi-AZ to distribute load

Answer

Run VACUUM to reclaim space

Question 4

A company is migrating a 500 GB MySQL database from on-premises to Amazon RDS for MySQL. The database is critical and must have minimal downtime. Which approach should be used to migrate the database with the least downtime?

Accepted Answer

Use AWS Database Migration Service (DMS) with a replication instance to perform a full load and then ongoing replication until cutover.. AWS DMS with ongoing replication (change data capture) is the correct approach because it performs an initial full load of the 500 GB database and then continuously replicates incremental changes from the source to the target RDS instance. This allows the source database to remain operational during migration, and the cutover can be performed in seconds by stopping application writes and applying the final changes, minimizing downtime to near zero.

Answer

Modify the on-premises database to use a new master user and then use the AWS Schema Conversion Tool to migrate.

Answer

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

Answer

Export the database using mysqldump and import into RDS using mysql command-line tool. Schedule a maintenance window for cutover.

Question 5

A company is deploying a new Amazon RDS for MariaDB instance. The database must be accessible from a specific set of EC2 instances in a VPC. How should the company configure security to allow access?

Accepted Answer

Create a security group for the RDS instance that allows inbound traffic from the EC2 instances' security group.. The recommended way to allow access from EC2 instances to an RDS instance is to create a security group for the RDS instance that allows inbound traffic on the database port from the security group attached to the EC2 instances. This leverages security group referencing, which is more secure and easier to manage than specifying IP addresses.

Option A is incorrect because while assigning the same security group to both could work, it is not a best practice as it would allow all members of that group to communicate without granularity, and it does not follow the principle of least privilege.

Option C is incorrect because IAM roles are used for authentication and authorization to AWS services, not for network-level access control. To access the RDS database, you still need to allow network traffic via a security group or NACL.

Option D is incorrect because network ACLs are stateless and operate at the subnet level. While they can be used, security groups are the preferred method for controlling traffic to an RDS instance because they are stateful and more granular.

Answer

Assign the same security group to both the RDS instance and the EC2 instances.

Answer

Attach an IAM role to the EC2 instances that grants access to the RDS database.

Answer

Configure a network ACL to allow inbound traffic from the EC2 instance IPs.

Question 6

A company is migrating an on-premises PostgreSQL database to Amazon RDS for PostgreSQL. The migration must have minimal downtime. Which TWO AWS services should be used together to achieve this?

Accepted Answer

AWS Database Migration Service (AWS DMS). AWS Database Migration Service (DMS) is used for the actual data migration with minimal downtime, supporting ongoing replication via change data capture (CDC) from the on-premises PostgreSQL database to Amazon RDS for PostgreSQL. AWS Schema Conversion Tool (SCT) is required to convert the source database schema and code to match the target RDS for PostgreSQL, identifying and resolving any compatibility issues. Together, SCT pre-processes the schema and DMS performs the data migration with replication, enabling a near-zero downtime migration.

Answer

AWS DataSync

Answer

AWS CloudEndure Migration

Answer

AWS Direct Connect

Question 7

A startup is building a mobile application that needs to store user profiles and preferences. The data is schema-less and will grow rapidly. The application requires single-digit millisecond latency for reads and writes. Which AWS database should they choose?

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is a fully managed NoSQL key-value and document database that delivers single-digit millisecond latency at any scale. It is schema-less, making it ideal for storing user profiles and preferences that have varying attributes, and it automatically scales to handle rapid growth without downtime or performance degradation.

Answer

Amazon Aurora (MySQL compatible)

Answer

Amazon Redshift

Answer

Amazon RDS for SQL Server

Question 8

Which TWO are valid use cases for Amazon ElastiCache for Redis? (Choose 2)

Accepted Answer

Session management for web applications. Amazon ElastiCache for Redis is an in-memory data store ideal for session management because it provides sub-millisecond latency for storing and retrieving session tokens, supports TTL-based key expiration to automatically clean up stale sessions, and offers atomic operations like SETEX for safe session creation. This makes it a perfect fit for stateless web applications that need to offload session state from the application server.

Answer

Storing graph data with relationships

Answer

Running complex analytical queries on large datasets

Answer

Persistent storage of relational data

Question 9

A company uses Amazon RDS for MySQL with read replicas. The application writes to the primary and reads from the replicas. Occasionally, the application reads stale data from the replicas. Which action would ensure read-after-write consistency without impacting write performance?

Accepted Answer

Configure the application to read from the primary instance for critical queries.. Using the primary instance for reads that require consistency ensures the application reads the latest data. Session-level replication checks are not supported in standard MySQL.

Answer

Set the replica_read_consistency parameter to 'session'.

Answer

Use the reader endpoint and increase the replica lag threshold.

Answer

Enable the 'rds_set_replication_status' parameter on the read replicas.

Question 10

A company needs to audit all SQL queries executed on an Amazon RDS for SQL Server database. Which AWS service should be used?

Accepted Answer

Amazon RDS Database Activity Streams. Amazon RDS Database Activity Streams provides a near real-time feed of database activity, including SQL queries, making it ideal for auditing all SQL queries on an RDS for SQL Server database. AWS CloudTrail (Option D) logs API calls to AWS services, not SQL queries. VPC Flow Logs (Option B) capture network traffic metadata, not database queries. Amazon CloudWatch Logs (Option C) can store and monitor logs but requires a log source; RDS does not natively send SQL logs to CloudWatch unless integrated with Database Activity Streams, which is the direct solution. Therefore, Option A is correct.

Answer

Amazon VPC Flow Logs

Answer

Amazon CloudWatch Logs

Answer

AWS CloudTrail

Question 11

A company runs an Amazon DynamoDB table with on-demand capacity. They notice that a specific partition key receives a high volume of read requests, causing throttling for that partition. What is the BEST solution to distribute the load evenly?

Accepted Answer

Add a random suffix to the partition key values to increase partition cardinality.. Adding a suffix to the partition key to create multiple partitions distributes read load across partitions.

Answer

Create a global secondary index with a different partition key.

Answer

Use DynamoDB Accelerator (DAX) to cache reads.

Answer

Switch the table to provisioned capacity with auto-scaling.

Question 12

A developer needs to restore an Amazon RDS for PostgreSQL DB instance to a specific point in time within the retention period. What must be enabled for this operation to be possible?

Accepted Answer

Automated backups with a retention period greater than 0.. Automated backups with a retention period greater than 0 are required for point-in-time recovery (PITR) in Amazon RDS. Option A is incorrect because deletion protection prevents accidental deletion but does not enable PITR. Option B is incorrect because read replicas are used for read scaling and disaster recovery, not for PITR. Option D is incorrect because Multi-AZ provides high availability but is not a prerequisite for PITR.

Answer

Deletion protection enabled.

Answer

A read replica in the same region.

Answer

Multi-AZ deployment.

Question 13

A company has a production Amazon Aurora MySQL DB cluster with one writer and two reader instances. The application uses a custom connection pool that uses the writer endpoint for all database calls. The application is experiencing increased latency during peak hours. A database specialist suggests using the reader endpoint for read-only queries. What change is required on the application side to implement this recommendation?

Accepted Answer

Update the application's connection logic to use the cluster endpoint for writes and the reader endpoint for reads.. The application needs to differentiate between read and write queries and send read queries to the reader endpoint while write queries continue to use the writer endpoint. No changes to the Aurora cluster are needed; Aurora automatically handles connectivity to reader instances via the reader endpoint. The cluster endpoint remains unchanged for writes.

Answer

Modify the Aurora cluster to enable load balancing for the reader endpoint.

Answer

Create a new custom endpoint for read-only queries and use it instead of the reader endpoint.

Answer

Replace the writer endpoint with the reader endpoint in the connection pool configuration.

Question 14

A company has an Amazon Redshift cluster that is running slowly on complex queries. The cluster has 10 dc2.large nodes. The 'QueryDuration' metric shows high values for several queries. The team wants to improve performance without changing queries. Which action is MOST likely to help?

Accepted Answer

Add more nodes of the same type to the cluster.. Adding more nodes (scaling out) increases the cluster's compute capacity, allowing complex queries to process data in parallel without any query changes. Option C is incorrect because Redshift Spectrum requires data to be in S3 and external tables to be defined, which would require modifying queries to reference those tables. Option B reduces storage I/O but not CPU-bound complex queries. Option D increasing concurrency can cause resource contention, slowing queries.

Answer

Enable compression on all columns.

Answer

Enable Redshift Spectrum to offload queries to Amazon S3.

Answer

Increase the workload management (WLM) concurrency level.

Question 15

A company is migrating its on-premises Oracle database to Amazon RDS for Oracle. The database is 2 TB in size and the network bandwidth is 100 Mbps. The migration must have minimal downtime. Which TWO approaches should be used together to achieve this?

Accepted Answer

Use AWS Database Migration Service (DMS) with ongoing replication to keep the target in sync.. AWS DMS with ongoing replication allows continuous data replication with minimal downtime. AWS Snowball can be used for the initial large data transfer to avoid prolonged network transfer. Option A (taking a full backup and restoring) would cause downtime; Option B (increasing bandwidth) is not feasible quickly; Option C (SCT) is for schema conversion, not data migration; Option D (DMS with ongoing replication) is correct; Option E (Snowball for initial load then DMS for ongoing changes) minimizes network transfer time.

Answer

Take a full backup of the source database and restore it to Amazon RDS.

Answer

Increase the network bandwidth to 1 Gbps to speed up the transfer.

Answer

Use AWS Schema Conversion Tool (SCT) to convert the schema before migration.