DBS-C01 Mock Exam 87 — 25 Questions

Question 1

The exhibit shows an IAM policy attached to a user. The user needs to create a manual snapshot of an RDS DB instance named 'production-db'. Which action will the user be able to perform?

Accepted Answer

Create a manual snapshot of 'production-db' with the name 'mydb-production-snapshot'.. The IAM policy allows CreateDBSnapshot only on DB instances with names starting with 'mydb-', and the snapshot name must also match the pattern 'mydb-*'. The snapshot name 'mydb-production-snapshot' satisfies that pattern. Option A is wrong because 'production-db-snapshot' does not start with 'mydb-'. Option C is wrong because the question asks about creating a snapshot, not describing instances. Option D is wrong because the policy does not grant DeleteDBInstance permission.

Answer

Create a manual snapshot of 'production-db' with the name 'production-db-snapshot'.

Answer

Describe the 'production-db' DB instance.

Answer

Delete the 'production-db' DB instance.

Question 2

A company is deploying a new Amazon DynamoDB table with global tables for a multi-region application. The application requires strongly consistent reads in the primary region and eventual consistency in secondary regions. Which write strategy should they use?

Accepted Answer

Use DynamoDB global tables with last writer wins (LWW) conflict resolution. DynamoDB global tables use last writer wins (LWW) conflict resolution based on the timestamp in the update, which automatically handles concurrent writes across regions. This strategy satisfies the requirement for strongly consistent reads in the primary region and eventual consistency in secondary regions, as global tables replicate data asynchronously and LWW ensures convergence without additional application logic.

Answer

Use conditional writes to ensure consistency

Answer

Use DynamoDB Streams to replicate writes to secondary regions

Answer

Use DynamoDB transactions across regions

Question 3

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database is 2 TB in size and has a tight migration window of 8 hours. Which THREE steps should be taken to minimize downtime during the migration?

Accepted Answer

Use AWS Database Migration Service (AWS DMS) with ongoing replication.. AWS DMS with ongoing replication (option C) allows continuous data replication from the source to the target, minimizing downtime during the final cutover. Disabling automated backups on the target RDS instance (option D) reduces I/O overhead and speeds up the migration process. Deploying a large RDS instance class (option E) provides higher network and disk throughput, accelerating the initial data load. Option A is incorrect because a manual snapshot is not used for migration, and option B is incorrect because AWS SCT is for schema conversion, not data replication.

Answer

Take a manual snapshot of the source database before migration.

Answer

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

Question 4

A company is migrating an on-premises PostgreSQL database to Amazon RDS for PostgreSQL. The database currently uses a custom extension that is not supported by RDS. The application relies heavily on this extension for advanced statistical analysis. Which design approach should the company take to minimize application changes?

Accepted Answer

Migrate to Amazon RDS for PostgreSQL and implement the extension's functionality using AWS Lambda functions called via triggers.. It allows the company to offload the unsupported custom extension's statistical analysis logic to AWS Lambda functions, which can be invoked via RDS PostgreSQL triggers. This approach minimizes application changes by keeping the database schema and query patterns largely intact, while the Lambda functions handle the advanced computations externally. RDS does not allow custom extensions, so this pattern leverages RDS for PostgreSQL's native trigger support to integrate with Lambda without modifying the application's core database interactions.

Answer

Migrate to PostgreSQL on Amazon EC2 and install the custom extension.

Answer

Migrate to Amazon DynamoDB and implement statistical analysis using DynamoDB streams and Lambda.

Answer

Migrate to Amazon RDS for PostgreSQL and install the custom extension on the RDS instance.

Question 5

A company is using Amazon DynamoDB with a global table that replicates data across two AWS Regions. The security team requires that all data be encrypted at rest with a customer-managed AWS KMS key. How should the company configure the KMS keys to meet this requirement?

Accepted Answer

Create a separate KMS key in each region and assign each replica table its regional KMS key.. For DynamoDB global tables, each replica table can use a different KMS key. You must create a KMS key in each region and configure the table to use the regional key. Option A is incorrect because a single KMS key cannot be used across regions; KMS keys are region-specific. Option B is incorrect because using the same key across regions is not possible. Option D is incorrect because DynamoDB global tables support encryption with customer managed keys.

Answer

Create a single KMS key in the primary region and use it for both replicas.

Answer

Use AWS managed encryption as DynamoDB does not support customer managed KMS keys for global tables.

Answer

Create a multi-Region KMS key and use it for both replicas.

Question 6

A company is running an Amazon DynamoDB table with provisioned capacity. The table has a partition key of 'user_id' and a sort key of 'timestamp'. The application performs frequent Query operations using the partition key and a range of sort keys. Recently, the 'ThrottledRequests' metric has spiked. The read and write capacity units are consistently at 80% utilization. What is the most effective way to resolve the throttling?

Accepted Answer

Change the partition key to a more uniformly distributed attribute. The throttling is likely due to uneven access patterns creating hot partitions. By changing the partition key to a more uniformly distributed attribute, the load is spread evenly across partitions, reducing throttling without needing to increase capacity. Option D is incorrect because enabling Auto Scaling with a higher target utilization delays scaling and can worsen throttling on hot partitions; it does not address the root cause. Option A is incorrect because increasing capacity may not help if a hot partition is throttled, and it increases costs. Option B is incorrect because adding a GSI does not reduce throttling on the base table; it only provides an alternative access pattern.

Answer

Increase the provisioned read and write capacity units

Answer

Add a global secondary index with a different partition key

Answer

Enable DynamoDB Auto Scaling with a higher target utilization

Question 7

A company is migrating a 3 TB PostgreSQL database to Amazon Aurora PostgreSQL. The migration must have minimal downtime. Which THREE steps should be taken?

Accepted Answer

Use AWS DMS with ongoing replication from the source PostgreSQL database. AWS DMS with ongoing replication (change data capture, CDC) allows continuous synchronization from the source PostgreSQL database to the target Aurora PostgreSQL cluster, enabling a cutover with minimal downtime. This is the standard approach for live migrations where the source remains fully operational during the transfer.

Answer

Disable autovacuum on the Aurora cluster to improve migration performance

Answer

Use AWS Snowball Edge to transfer the data offline

Question 8

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

Accepted Answer

AWS Database Migration Service (DMS). AWS Database Migration Service (DMS) is the correct choice because it supports ongoing replication from an on-premises PostgreSQL source to Amazon RDS for PostgreSQL, enabling near-zero downtime migrations. DMS uses change data capture (CDC) to continuously replicate transactions after an initial full load, allowing the target database to stay synchronized until cutover.

Answer

AWS Snowball

Answer

AWS CloudEndure Migration

Answer

AWS Direct Connect

Question 9

A company is deploying a MongoDB-compatible database using Amazon DocumentDB. The application requires the ability to perform ad-hoc queries on nested fields within documents. Which DocumentDB feature should be enabled to meet this requirement?

Accepted Answer

Indexes on nested fields. Amazon DocumentDB supports indexing on nested fields, which allows efficient querying of sub-documents and arrays within documents. By creating indexes on specific nested paths (e.g., "address.city"), the query engine can perform index scans instead of full collection scans, enabling fast ad-hoc queries on nested fields. This feature directly meets the requirement for ad-hoc queries on nested fields.

Answer

TTL indexes

Answer

Transactions

Answer

Change streams

Question 10

A company wants to migrate a 1 TB on-premises PostgreSQL database to Amazon RDS for PostgreSQL. They have a limited internet bandwidth. Which service should they use to accelerate the migration?

Accepted Answer

AWS Snowball Edge. AWS Snowball Edge is the correct choice because it provides a physical storage device that can be used to transfer large volumes of data (1 TB) over a limited internet bandwidth. By shipping the device to AWS, the initial bulk data load bypasses the internet entirely, which accelerates the migration. After the data is loaded into Amazon RDS for PostgreSQL via Snowball Edge, AWS DMS can be used for ongoing replication to keep the database in sync.

Answer

AWS Database Migration Service (DMS)

Answer

Amazon S3

Answer

AWS Direct Connect

Question 11

An administrator is deploying an Amazon RDS for MySQL DB instance and needs to ensure that all connections use SSL. Which parameter should be set on the RDS DB instance?

Accepted Answer

Set require_secure_transport=ON in the DB parameter group. Setting `require_secure_transport=ON` in the DB parameter group enforces that all connections to the RDS MySQL DB instance must use SSL/TLS. This parameter, supported by MySQL 5.7 and later, rejects any non-encrypted connection attempt, ensuring transport layer security for all client-server communication.

Answer

Set ssl_cipher in the DB parameter group

Answer

Set tls_version in the DB parameter group

Answer

Set rds.force_ssl=1 in the DB parameter group

Question 12

A company uses Amazon DynamoDB Global Tables with strong consistent reads. They notice that a write to us-east-1 is not visible in eu-west-1 after several seconds. Which configuration setting is MOST likely causing this behavior?

Accepted Answer

DynamoDB Streams is not enabled on the table. DynamoDB Global Tables require DynamoDB Streams to be enabled on the table. If streams are disabled, write operations in one region will not be replicated to other regions, causing the writes to never become visible. This matches the symptom of writes not appearing after several seconds. Option B (Auto Scaling) does not affect replication. Option C (LWW conflict resolution) is enabled by default and does not cause delays. Option D (strongly consistent reads) are not supported on Global Tables and would generate an error, not a delay.

Answer

Auto Scaling is configured for write capacity

Answer

Last writer wins (LWW) conflict resolution is disabled

Answer

Strongly consistent reads are used on a global table

Question 13

An application is experiencing increased latency when writing to an Amazon DynamoDB table. The table uses on-demand capacity mode. The CloudWatch metric 'WriteThrottleEvents' is zero. What is the most likely cause of the increased latency?

Accepted Answer

A hot partition is causing excessive write traffic to a single partition.. On-demand DynamoDB tables can experience throttling if you exceed the previous peak traffic by more than double in a short time, but since WriteThrottleEvents is zero, the latency is likely due to a hot partition causing uneven traffic distribution. Option A is incorrect because on-demand capacity does not use WCUs; throughput is automatically scaled. Option B is incorrect because DynamoDB Accelerator (DAX) is a read cache and does not affect write latency. Option D is incorrect because on-demand tables do not have provisioned capacity; throttling would be indicated by WriteThrottleEvents, which is zero.

Answer

The write capacity units (WCUs) are set too low.

Answer

DynamoDB Accelerator (DAX) is not configured for writes.

Answer

The table is experiencing write throttling due to exceeding the provisioned write capacity.

Question 14

A company is using Amazon DynamoDB for a shopping cart application. The table has a partition key of `user_id` and a sort key of `item_id`. The application performs frequent updates to the `quantity` attribute. The company notices that write requests are being throttled during peak hours. Which TWO actions would help reduce throttling? (Choose two.)

Accepted Answer

Increase the provisioned write capacity for the table.. Increasing the provisioned write capacity directly raises the number of write capacity units (WCUs) available per second, allowing more write requests to succeed without being throttled. Since the application performs frequent updates to the `quantity` attribute, which consumes write capacity, adding more capacity alleviates throttling during peak hours.

Answer

Use conditional writes to prevent overwrites.

Answer

Enable DynamoDB Streams to process writes asynchronously.

Answer

Enable DynamoDB Accelerator (DAX) for the table.

Question 15

A database administrator runs the command shown in the exhibit. The security team requires that the database be encrypted at rest. What should the administrator do to enable encryption?

Accepted Answer

Create a snapshot of the DB instance, copy the snapshot with encryption, and restore from the encrypted snapshot.. Encryption cannot be enabled on an existing unencrypted instance; you must create a snapshot, copy it with encryption, and restore. Option A is wrong because encryption is at the storage level, not table level. Option C is wrong because modifying the instance does not add encryption. Option D is wrong because the command shows StorageEncrypted is false, so it is not encrypted.

Answer

Enable encryption at the table level using MySQL's built-in encryption.

Answer

Modify the DB instance and set StorageEncrypted to true.

Answer

The instance is already encrypted because the output shows 'StorageEncrypted' as false.

Question 16

A company uses Amazon DynamoDB to store IoT sensor data. Each sensor sends data every second, and the application needs to query the latest reading from each sensor. The sensor ID is the partition key, and the timestamp is the sort key. The table has millions of sensors. Which query pattern is most efficient to get the latest reading for a specific sensor?

Accepted Answer

Use Query with KeyConditionExpression on sensor ID, ScanIndexForward=false, Limit=1. Query with ScanIndexForward=false and Limit=1 retrieves only the most recent item for a given partition key (sensor ID) by reading items in descending sort key (timestamp) order and stopping after one item. This is the most efficient pattern as it uses the primary key index directly, avoids scanning, and minimizes read capacity consumption.

Answer

Use BatchGetItem with the sensor ID and multiple timestamps

Answer

Use Scan with FilterExpression on sensor ID

Answer

Use GetItem with the sensor ID and the current timestamp

Question 17

A financial services company uses Amazon Aurora MySQL-Compatible Edition for transaction processing. They need to run complex analytical queries on the same data without impacting transactional performance. Which solution meets these requirements?

Accepted Answer

Use Aurora Zero-ETL integration with Amazon Redshift. Aurora Zero-ETL integration with Amazon Redshift allows you to run complex analytical queries on transactional data without impacting Aurora's performance. It eliminates the need for extract, transform, and load (ETL) pipelines by automatically replicating data from Aurora to Redshift in near real-time, ensuring that analytical workloads are offloaded to a separate, optimized analytics engine.

Answer

Enable Performance Insights and use RDS Proxy

Answer

Export data to Amazon S3 and query with Athena

Answer

Create an Aurora Replica and run analytical queries against it

Question 18

A company is migrating a 500 GB MongoDB database to Amazon DocumentDB. The migration is done using AWS DMS with full load and ongoing replication. The full load completes successfully, but during CDC, the DMS task logs show 'Memory limit exceeded' errors and the task fails repeatedly. The DMS replication instance is a dms.r5.large. The source MongoDB has a write-heavy workload with many small updates. The DBA needs to fix the migration without restarting from scratch. Which action should the DBA take?

Accepted Answer

Increase the DMS replication instance size to a larger instance class with more memory.. The 'Memory limit exceeded' error during CDC with a write-heavy workload indicates the replication instance lacks sufficient memory to buffer the changes. Increasing the instance size (e.g., to dms.r5.xlarge) provides more memory. Option B is wrong because reducing BatchApplyEnabled may slow down apply but does not increase memory; it could even worsen the backlog. Option C is wrong because restarting just clears cache temporarily; the error will recur. Option D is wrong because Multi-AZ provides high availability, not additional memory.

Answer

Reduce the DMS task's 'BatchApplyEnabled' setting to apply transactions individually.

Answer

Stop and restart the DMS task to clear the cache.

Answer

Enable Multi-AZ on the DMS replication instance to distribute the load.

Question 19

A healthcare application stores patient records in Amazon DynamoDB. Each record has a unique patient ID and contains sensitive health information. The application must encrypt data at rest and ensure that only authorized services can access the data. Which combination of design choices meets these requirements?

Accepted Answer

Enable DynamoDB encryption at rest using AWS KMS and use IAM policies to restrict access.. DynamoDB encryption at rest using AWS KMS provides server-side encryption for sensitive patient data, while IAM policies allow fine-grained access control to ensure only authorized services can access the table. This combination directly meets both the encryption and access control requirements without unnecessary complexity or service mismatches.

Answer

Implement client-side encryption and use Lambda to validate access.

Answer

Enable S3 server-side encryption with AWS KMS and use bucket policies.

Answer

Use AWS CloudHSM for key storage and VPC endpoints for access control.

Question 20

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).. AWS DMS with ongoing replication (CDC) is the correct approach because it allows you to perform an initial full load of the 2 TB database while continuously capturing and applying changes from the source MySQL database. This minimizes downtime by keeping the target Aurora MySQL cluster nearly synchronized, and you only need to stop writes briefly during the final cutover to ensure data consistency.

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.