Amazon Amazon Certifications DBS-C01 Questions & Answers

• Question 311:

  A media company hosts a highly available news website on AWS but needs to improve its page load time, especially during very popular news releases. Once a news page is published, it is very unlikely to change unless an error is identified. The company has decided to use Amazon ElastiCache.

  What is the recommended strategy for this use case?

  A. Use ElastiCache for Memcached with write-through and long time to live (TTL)

  B. Use ElastiCache for Redis with lazy loading and short time to live (TTL)

  C. Use ElastiCache for Memcached with lazy loading and short time to live (TTL)

  D. Use ElastiCache for Redis with write-through and long time to live (TTL)

  Correct Answer: A

  Explanation: The recommended strategy for this use case is option A: use ElastiCache for Memcached with write-through and long time to live (TTL).

  Amazon ElastiCache is a fully managed in-memory data store service that supports two open source engines: Memcached and Redis. Amazon ElastiCache can be used to improve the performance and scalability of web applications by caching frequently accessed data in memory, reducing the load and latency of database queries. Memcached and Redis have different features and use cases. Memcached is a simple, high-performance, distributed caching system that supports a large number of concurrent connections and large object sizes. Redis is an advanced, feature-rich, in-memory data structure store that supports data persistence, replication, transactions, pub/sub, Lua scripting, and various data types. For this use case, Memcached is more suitable than Redis because the news website does not need the advanced features of Redis, such as data persistence or replication. The news website only needs a fast and simple caching solution that can handle high traffic and large objects. Write-through and lazy loading are two common caching strategies that determine when and how data is written to the cache. Write-through is a strategy that writes data to the cache whenever it is written to the database. Lazy loading is a strategy that writes data to the cache only when it is requested for the first time. For this use case, write-through is more suitable than lazy loading because the news website needs to improve its page load time, especially during very popular news releases. Write-through ensures that the cache always has the most up-to-date data and avoids cache misses or stale data. Lazy loading may cause cache misses or stale data if the data is not cached or updated in time. Time to live (TTL) is a parameter that specifies how long an item can remain in the cache before it expires and is deleted. TTL can be used to control the cache size and freshness. For this use case, long TTL is more suitable than short TTL because the news website has a low probability of changing its data once a news page is published. Long TTL allows the data to stay in the cache longer and reduces the frequency of cache updates or evictions. Short TTL may cause unnecessary cache updates or evictions if the data does not change frequently. Therefore, option A is the recommended strategy for this use case because it uses ElastiCache for Memcached with write-through and long TTL, which provides a fast and simple caching solution that can handle high traffic and large objects, and ensures that the cache always has the most up-to-date and relevant data.

• Question 312:

  A stock market analysis firm maintains two locations: one in the us-east-1 Region and another in the eu-west-2 Region. The business want to build an AWS database solution capable of providing rapid and accurate updates.

  Dashboards with advanced analytical queries are used to present data in the eu-west-2 office. Because the corporation will use these dashboards to make purchasing choices, they must have less than a second to obtain application data.

  Which solution satisfies these criteria and gives the MOST CURRENT dashboard?

  A. Deploy an Amazon RDS DB instance in us-east-1 with a read replica instance in eu- west-2. Create an Amazon ElastiCache cluster in eu-west-2 to cache data from the read replica to generate the dashboards.

  B. Use an Amazon DynamoDB global table in us-east-1 with replication into eu-west-2. Use multi-active replication to ensure that updates are quickly propagated to eu-west-2.

  C. Use an Amazon Aurora global database. Deploy the primary DB cluster in us-east-1. Deploy the secondary DB cluster in eu-west-2. Configure the dashboard application to read from the secondary cluster.

  D. Deploy an Amazon RDS for MySQL DB instance in us-east-1 with a read replica instance in eu-west-2. Configure the dashboard application to read from the read replica.

  Correct Answer: C

  Explanation: Amazon Aurora global databases span multiple AWS Regions, enabling low latency global reads and providing fast recovery from the rare outage that might affect an entire AWS Region. An Aurora global database has a primary DB cluster in one Region, and up to five secondary DB clusters in different Regions. https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/aurora-global- database.html

• Question 313:

  A company has applications running on Amazon EC2 instances in a private subnet with no internet connectivity. The company deployed a new application that uses Amazon DynamoDB, but the application cannot connect to the DynamoDB tables. A developer already checked that all permissions are set correctly.

  What should a database specialist do to resolve this issue while minimizing access to external resources?

  A. Add a route to an internet gateway in the subnet's route table.

  B. Add a route to a NAT gateway in the subnet's route table.

  C. Assign a new security group to the EC2 instances with an outbound rule to ports 80 and 443.

  D. Create a VPC endpoint for DynamoDB and add a route to the endpoint in the subnet's route table.

  Correct Answer: D

  Explanation: https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/vpc- endpoints-dynamodb.html

• Question 314:

  A company is due for renewing its database license. The company wants to migrate its 80 TB transactional database system from on-premises to the AWS Cloud. The migration should incur the least possible downtime on the downstream database applications. The company's network infrastructure has limited network bandwidth that is shared with other applications.

  Which solution should a database specialist use for a timely migration?

  A. Perform a full backup of the source database to AWS Snowball Edge appliances and ship them to be loaded to Amazon S3. Use AWS DMS to migrate change data capture (CDC) data from the source database to Amazon S3. Use a second AWS DMS task to migrate all the S3 data to the target database.

  B. Perform a full backup of the source database to AWS Snowball Edge appliances and ship them to be loaded to Amazon S3. Periodically perform incremental backups of the source database to be shipped in another Snowball Edge appliance to handle syncing change data capture (CDC) data from the source to the target database.

  C. Use AWS DMS to migrate the full load of the source database over a VPN tunnel using the internet for its primary connection. Allow AWS DMS to handle syncing change data capture (CDC) data from the source to the target database.

  D. Use the AWS Schema Conversion Tool (AWS SCT) to migrate the full load of the source database over a VPN tunnel using the internet for its primary connection. Allow AWS SCT to handle syncing change data capture (CDC) data from the source to the target database.

  Correct Answer: A

  Explanation: https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Target.S3.html Using Amazon S3 as a target for AWS Database Migration Service

• Question 315:

  A company has deployed an e-commerce web application in a new AWS account. An Amazon RDS for MySQL Multi-AZ DB instance is part of this deployment with a database- 1.xxxxxxxxxxxx.us-east- 1.rds.amazonaws.com endpoint listening on port 3306. The company's Database Specialist is able to log in to MySQL and run queries from the bastion host using these details.

  When users try to utilize the application hosted in the AWS account, they are presented with a generic error message. The application servers are logging a "could not connect to server: Connection times out" error message to Amazon CloudWatch Logs.

  What is the cause of this error?

  A. The user name and password the application is using are incorrect.

  B. The security group assigned to the application servers does not have the necessary rules to allow inbound connections from the DB instance.

  C. The security group assigned to the DB instance does not have the necessary rules to allow inbound connections from the application servers.

  D. The user name and password are correct, but the user is not authorized to use the DB instance.

  Correct Answer: C

  Reference: https://forums.aws.amazon.com/thread.jspa?threadID=129700

• Question 316:

  A software development company is using Amazon Aurora MySQL DB clusters for several use cases, including development and reporting. These use cases place unpredictable and varying demands on the Aurora DB clusters, and can cause momentary spikes in latency. System users run ad-hoc queries sporadically throughout the week. Cost is a primary concern for the company, and a solution that does not require significant rework is needed.

  Which solution meets these requirements?

  A. Create new Aurora Serverless DB clusters for development and reporting, then migrate to these new DB clusters.

  B. Upgrade one of the DB clusters to a larger size, and consolidate development and reporting activities on this larger DB cluster.

  C. Use existing DB clusters and stop/start the databases on a routine basis using scheduling tools.

  D. Change the DB clusters to the burstable instance family.

  Correct Answer: A

  https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/Concepts.DBInstance Class.html

• Question 317:

  A company uses a large, growing, and high performance on-premises Microsoft SQL Server instance With an Always On availability group cluster size of 120 TIE. The company uses a third-party backup product that requires system-level access to the databases. The company will continue to use this third-party backup product in the future.

  The company wants to move the DB cluster to AWS with the least possible downtime and data loss. The company needs a 2 Gbps connection to sustain Always On asynchronous data replication between the company's data center and AWS.

  Which combination of actions should a database specialist take to meet these requirements? (Select THREE.)

  A. Establish an AWS Direct Connect hosted connection between the companfs data center and AWS

  B. Create an AWS Site-to-Site VPN connection between the companVs data center and AWS over the internet

  C. Use AWS Database Migration Service (AWS DMS) to migrate the on-premises SQL Server databases to Amazon RDS for SQL Server Configure Always On availability groups for SQL Server.

  D. Deploy a new SQL Server Always On availability group DB cluster on Amazon EC2 Configure Always On distributed availability groups between the on-premises DB cluster and the AWS DB cluster_ Fail over to the AWS DB cluster when it is time to migrate.

  E. Grant system-level access to the third-party backup product to perform backups of the Amazon RDS for SQL Server DB instance.

  F. Configure the third-party backup product to perform backups of the DB cluster on Amazon EC2.

  Correct Answer: ADF

  The best combination of actions to meet the company's requirements are:

  A. Establish an AWS Direct Connect hosted connection between the company's data center and AWS. This will provide a secure and high-bandwidth connection for the Always On data replication and minimize the network latency and data loss. D. Deploy a new SQL Server Always On availability group DB cluster on Amazon EC2. Configure Always On distributed availability groups between the on-premises DB cluster and the AWS DB cluster. Fail over to the AWS DB cluster when it is time to migrate. This will allow the company to use the same SQL Server version and edition as on-premises, and leverage the distributed availability group feature to span two separate availability groups across different locations. The failover process will be fast and seamless, with minimal downtime and data loss. F. Configure the third-party backup product to perform backups of the DB cluster on Amazon EC2. This will enable the company to continue using their existing backup solution, which requires system-level access to the databases. Amazon RDS for SQL Server does not support system-level access, so it is not a suitable option for this requirement.

• Question 318:

  A Database Specialist is constructing a new Amazon Neptune DB cluster and tries to load data from Amazon S3 using the Neptune bulk loader API. The Database Specialist is confronted with the following error message:

  Unable to establish a connection to the s3 endpoint. The source URL is s3:/mybucket/graphdata/ and the region code is us-east-1. Kindly confirm your Configuration S3.

  Which of the following activities should the Database Specialist take to resolve the issue? (Select two.)

  A. Check that Amazon S3 has an IAM role granting read access to Neptune

  B. Check that an Amazon S3 VPC endpoint exists

  C. Check that a Neptune VPC endpoint exists

  D. Check that Amazon EC2 has an IAM role granting read access to Amazon S3

  E. Check that Neptune has an IAM role granting read access to Amazon S3

  Correct Answer: BE

  Explanation: https://docs.aws.amazon.com/neptune/latest/userguide/bulk-load-tutorial- IAM.html https://docs.aws.amazon.com/neptune/latest/userguide/bulk-load-data.html

  "An IAM role for the Neptune DB instance to assume that has an IAM policy that allows access to the data files in the S3 bucket. The policy must grant Read and List permissions." "An Amazon S3 VPC endpoint. For more information, see the Creating an Amazon S3 VPC Endpoint section."

• Question 319:

  A company is using an Amazon Aurora PostgreSQL DB cluster for the backend of its mobile application. The application is running continuously and a database specialist is satisfied with high availability and fast failover, but is concerned about performance degradation after failover.

  How can the database specialist minimize the performance degradation after failover?

  A. Enable cluster cache management for the Aurora DB cluster and set the promotion priority for the writer DB instance and replica to tier-0

  B. Enable cluster cache management tor the Aurora DB cluster and set the promotion priority for the writer DB instance and replica to tier-1

  C. Enable Query Plan Management for the Aurora DB cluster and perform a manual plan capture

  D. Enable Query Plan Management for the Aurora DB cluster and force the query optimizer to use the desired plan

  Correct Answer: A

  Explanation:

• Question 320:

  A company has a web-based survey application that uses Amazon DynamoDB. During peak usage, when survey responses are being collected, a Database Specialist sees the ProvisionedThroughputExceededException error.

  What can the Database Specialist do to resolve this error? (Choose two.)

  A. Change the table to use Amazon DynamoDB Streams

  B. Purchase DynamoDB reserved capacity in the affected Region

  C. Increase the write capacity units for the specific table

  D. Change the table capacity mode to on-demand

  E. Change the table type to throughput optimized

  Correct Answer: CD

  https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/switching.capacity mode.html