SAA-C03 VCE Exam Download

A write-through caching strategy adds or updates data in the cache whenever data is written to the database. This ensures that the data in the cache is always consistent with the data in the database. A write-through caching strategy also reduces the cache miss penalty, as data is always available in the cache when it is requested. However, a write-through caching strategy can increase the write latency, as data has to be written to both the cache and the database. A write-through caching strategy is suitable for applications that require high data consistency and low read latency.

A lazy loading caching strategy only loads data into the cache when it is requested, and updates the cache when there is a cache miss. This can result in stale data in the cache, as data is not updated in the cache when it is changed in the database. A lazy loading caching strategy is suitable for applications that can tolerate some data inconsistency and have a low cache miss rate.

An adding TTL caching strategy assigns a time-to-live (TTL) value to each data item in the cache, and removes the data from the cache when the TTL expires. This can help prevent stale data in the cache, as data is periodically refreshed from the database. However, an adding TTL caching strategy can also increase the cache miss rate, as data can be evicted from the cache before it is requested. An adding TTL caching strategy is suitable for applications that have a high cache hit rate and can tolerate some data inconsistency.

An AWS AppConfig caching strategy is not a valid option, as AWS AppConfig is a service that enables customers to quickly deploy validated configurations to applications of any size and scale. AWS AppConfig does not provide a caching layer for web applications.

References: Caching strategies - Amazon ElastiCache, Caching for high-volume workloads with Amazon ElastiCache

To meet the requirements of the use case in a cost-effective way, the following steps are recommended:

Deploy an AWS Storage Gateway on premises in Amazon S3 File Gateway mode. This will allow the company to write the .csv files generated by the devices to an SMB file share, which will be stored as objects in Amazon S3 buckets. AWS Storage Gateway is a hybrid cloud storage service that integrates on-premises environments with AWS storage. Amazon S3 File Gateway mode provides a seamless way to connect to Amazon S3 and access a virtually unlimited amount of cloud storage1.

Set up an AWS Glue crawler to create a table based on the data that is in Amazon S3. This will enable the company to use standard SQL to query the data stored in Amazon S3 buckets. AWS Glue is a serverless data integration service that simplifies data preparation and analysis. AWS Glue crawlers can automatically discover and classify data from various sources, and create metadata tables in the AWS Glue Data Catalog2. The Data Catalog is a central repository that stores information about data sources and how to access them3.

Set up Amazon Athena to query the data that is in Amazon S3. This will provide the company analysts with a serverless and interactive query service that can analyze data directly in Amazon S3 using standard SQL. Amazon Athena is integrated with the AWS Glue Data Catalog, so users can easily point Athena at the data source tables defined by the crawlers. Amazon Athena charges only for the queries that are run, and offers a pay-per-query pricing model, which makes it a cost-effective option for periodic queries4.

The other options are not correct because they are either not cost-effective or not suitable for the use case. Deploying an AWS Storage Gateway on premises in Amazon FSx File Gateway mode is not correct because this mode provides low-latency access to fully managed Windows file shares in AWS, which is not required for the use case. Setting up an Amazon EMR cluster with EMR File System (EMRFS) to query the data that is in Amazon S3 is not correct because this option involves setting up and managing a cluster of EC2 instances, which adds complexity and cost to the solution. Setting up an Amazon Redshift cluster to query the data that is in Amazon S3 is not correct because this option also involves provisioning and managing a cluster of nodes, which adds overhead and cost to the solution.

References:

What is AWS Storage Gateway?

What is AWS Glue?

AWS Glue Data Catalog

What is Amazon Athena?

These options are the most suitable ways to design a shared storage solution for a web application that is deployed across multiple Availability Zones and requires strong consistency. Option B uses Amazon Elastic File System (Amazon EFS) as a shared file system that can be mounted on multiple EC2 instances in different Availability Zones. Amazon EFS provides high availability, durability, scalability, and performance for file-based workloads. It also supports strong consistency, which means that any changes made to the file system are immediately visible to all clients. Option E uses Amazon S3 as a shared object store that can store the web content and serve it through Amazon CloudFront, a content delivery network (CDN). Amazon S3 provides high availability, durability, scalability, and performance for object-based workloads. It also supports strong consistency for read-after-write and list operations, which means that any changes made to the objects are immediately visible to all clients. By setting the metadata for the Cache-Control header to no-cache, the web content can be prevented from being cached by the browsers or the CDN edge locations, ensuring that the latest content is always delivered to the users.

Option A is not suitable because using AWS Storage Gateway Volume Gateway as a shared storage solution for a web application is not efficient or scalable. AWS Storage Gateway Volume Gateway is a hybrid cloud storage service that provides block storage volumes that can be mounted on-premises or on EC2 instances as iSCSI devices. It is useful for migrating or backing up data to AWS, but it is not designed for serving web content or providing strong consistency. Moreover, using Volume Gateway would incur additional costs and complexity, and it would not leverage the native AWS storage services.

Option C is not suitable because creating a shared Amazon EBS volume and mounting it on multiple EC2 instances is not possible or reliable. Amazon EBS is a block storage service that provides persistent and high-performance volumes for EC2 instances. However, EBS volumes can only be attached to one EC2 instance at a time, and they are constrained to a single Availability Zone. Therefore, creating a shared EBS volume for a web application that is deployed across multiple Availability Zones is not feasible. Moreover, EBS volumes do not support strong consistency, which means that any changes made to the volume may not be immediately visible to other clients.

Option D is not suitable because using AWS DataSync to perform continuous synchronization of data between EC2 hosts in the Auto Scaling group is not efficient or scalable. AWS DataSync is a data transfer service that helps you move large amounts of data to and from AWS storage services. It is useful for migrating or archiving data, but it is not designed for serving web content or providing strong consistency. Moreover, using DataSync would incur additional costs and complexity, and it would not leverage the native AWS storage services. References:

What Is Amazon Elastic File System?

What Is Amazon Simple Storage Service?

What Is Amazon CloudFront?

What Is AWS Storage Gateway?

What Is Amazon Elastic Block Store?

What Is AWS DataSync?

To migrate the DNS hosting service to a more resilient managed DNS service on AWS, the company should use Amazon Route 53, which is a highly available and scalable cloud DNS web service. Route 53 can host public DNS records for the company’s domain name and provide reliable and secure DNS resolution. To rapidly migrate the DNS hosting service, the company should create a public hosted zone for the domain name in Route 53, which is a container for the domain’s DNS records. Then, the company should import the zone file containing the domain records hosted by the previous provider, which is a text file that defines the DNS records for the domain. This way, the company can quickly transfer the existing DNS records to Route 53 without manually creating them. After importing the zone file, the company should update the domain registrar to use the name servers that Route 53 assigns to the hosted zone. This will ensure that DNS queries for the domain name are routed to Route 53 and resolved by the imported records.