AWS CloudFront

CloudFront

  • CloudFront is a fully managed, fast content delivery network (CDN) service that speeds up the distribution of static, dynamic web or streaming content to end-users.
  • CloudFront delivers the content through a worldwide network of data centers called edge locations or Point of Presence (POP).
  • CloudFront securely delivers data, videos, applications, and APIs to customers globally with low latency, high transfer speeds, all within a developer-friendly environment.
  • CloudFront gives businesses and web application developers an easy and cost-effective way to distribute content with low latency and high data transfer speeds.
  • CloudFront speeds up the distribution of the content by routing each user request to the edge location that can best serve the content thus providing the lowest latency (time delay).
  • CloudFront uses the AWS backbone network that dramatically reduces the number of network hops that users’ requests must pass through and helps improves performance, provide lower latency and higher data transfer rate
  • CloudFront is a good choice for the distribution of frequently accessed static content that benefits from edge delivery – like popular website images, videos, media files, or software downloads

CloudFront Benefits

  • CloudFront eliminates the expense and complexity of operating a network of cache servers in multiple sites across the internet and eliminates the need to over-provision capacity in order to serve potential spikes in traffic.
  • CloudFront also provides increased reliability and availability because copies of objects are held in multiple edge locations around the world.
  • CloudFront keeps persistent connections with the origin servers so that those files can be fetched from the origin servers as quickly as possible.
  • CloudFront also uses techniques such as collapsing simultaneous viewer requests at an edge location for the same file into a single request to the origin server reducing the load on the origin.
  • CloudFront offers the most advanced security capabilities, including field-level encryption and HTTPS support.
  • CloudFront seamlessly integrates with AWS Shield, AWS Web Application Firewall – WAF, and Route 53 to protect against multiple types of attacks including network and application layer DDoS attacks.

Edge Locations & Regional Edge Caches

  • CloudFront Edge Locations or POPs make sure that popular content can be served quickly to the viewers.
  • CloudFront also has Regional Edge Caches that help bring more content closer to the viewers, even when the content is not popular enough to stay at a POP, to help improve performance for that content.
  • Regional Edge Caches are deployed globally, close to the viewers, and are located between the origin servers and the Edge Locations.
  • Regional edge caches support multiple Edge Locations and support a larger cache size so objects remain in the cache longer at the nearest regional edge cache location.
  • Regional edge caches help with all types of content, particularly content that tends to become less popular over time.

Configuration & Content Delivery

CloudFront Configuration and Content Delivery

Configuration

  1. Origin servers need to be configured to get the files for distribution. An origin server stores the original, definitive version of the objects and can be an AWS hosted service for e.g. S3, EC2, or an on-premise server
  2. Files or objects can be added/uploaded to the Origin servers with public read permissions or permissions restricted to Origin Access Identity (OAI).
  3. Create a CloudFront distribution, which tells CloudFront which origin servers to get the files from when users request the files.
  4. CloudFront sends the distribution configuration to all the edge locations.
  5. The website can be used with the CloudFront provided domain name or a custom alternate domain name.
  6. An origin server can be configured to limit access protocols, caching behaviour, add headers to the files to add TTL, or the expiration time.

Content delivery to Users

  1. When a user accesses the website, file, or object – the DNS routes the request to the CloudFront edge location that can best serve the user’s request with the lowest latency.
  2. CloudFront returns the object immediately if the requested object is present in the cache at the Edge location.
  3. If the requested object does not exist in the cache at the edge location, the POP typically goes to the nearest regional edge cache to fetch it.
  4. If the object is in the regional edge cache, CloudFront forwards it to the POP that requested it.
  5. For objects not cached at either the POP or the regional edge cache location, CloudFront requests the object from the origin server and returns it to the user via the regional edge cache and POP
  6. CloudFront begins to forward the object to the user as soon as the first byte arrives from the regional edge cache location.
  7. CloudFront also adds the object to the cache in the regional edge cache location in addition to the POP for the next time a viewer requests it.
  8. When the object reaches its expiration time, for any new request CloudFront checks with the Origin server for any latest versions, if it has the latest it uses the same object. If the Origin server has the latest version the same is retrieved, served to the user, and cached as well

CloudFront Origins

  • Each origin is either an S3 bucket, a MediaStore container, a MediaPackage channel, or a custom origin like an EC2 instance or an HTTP server
  • For the S3 bucket, use the bucket URL or the static website endpoint URL, and the files either need to be publicly readable or secured using OAI.
  • Origin restrict access, for S3 only, can be configured using Origin Access Identity to prevent direct access to the S3 objects.
  • For the HTTP server as the origin, the domain name of the resource needs to be mapped and files must be publicly readable.
  • Distribution can have multiple origins for each bucket with one or more cache behaviors that route requests to each origin. Path pattern in a cache behavior determines which requests are routed to the origin (S3 bucket) that is associated with that cache behavior.
  • Origin Groups can be used to specify two origins to configure origin failover for high availability. Origin failover can be used to designate a primary origin plus a second origin that CloudFront automatically switches to when the primary origin returns specific HTTP status code failure responses.

CloudFront Delivery Methods

Web distributions

  • supports both static and dynamic content for e.g. HTML, CSS, js, images, etc using HTTP or HTTPS.
  • supports multimedia content on-demand using progressive download and Apple HTTP Live Streaming (HLS).
  • supports a live event, such as a meeting, conference, or concert, in real-time. For live streaming, distribution can be created automatically using an AWS CloudFormation stack.
  • origin servers can be either an S3 bucket or an HTTP server, for e.g., a web server or an AWS ELB, etc.

RMTP distributions (Support Discontinued)

  • supports streaming of media files using Adobe Media Server and the Adobe Real-Time Messaging Protocol (RTMP)
  • must use an S3 bucket as the origin.
  • To stream media files using CloudFront, two types of files are needed
    • Media files
    • Media player for e.g. JW Player, Flowplayer, or Adobe flash
  • End-users view media files using the media player that is provided; not the locally installed on the computer of the device
  • When an end-user streams the media file, the media player begins to play the file content while the file is still being downloaded from CloudFront.
  • The media file is not stored locally on the end user’s system.
  • Two CloudFront distributions are required, Web distribution for media Player and RMTP distribution for media files
  • Media player and Media files can be stored in a same-origin S3 bucket or different buckets

Cache Behavior Settings

Path Patterns

  • Path Patterns help define which path the Cache behaviour would apply to.
  • A default (*) pattern is created and multiple cache distributions can be added with patterns to take priority over the default path.

Viewer Protocol Policy (Viewer -> CloudFront)

  • Viewer Protocol policy can be configured to define the allowed access protocol.
  • Between CloudFront & Viewers, cache distribution can be configured to either allow
    • HTTPS only – supports HTTPS only
    • HTTP and HTTPS – supports both
    • HTTP redirected to HTTPS – HTTP is automatically redirected to HTTPS

Origin Protocol Policy (CloudFront -> Origin)

  • Between CloudFront & Origin, cache distribution can be configured with
    • HTTP only (for S3 static website).
    • HTTPS only – CloudFront fetches objects from the origin by using HTTPS.
    • Match Viewer – CloudFront uses the protocol that the viewer used to request the objects.
  • For S3 as origin,
    • For the website, the protocol has to be HTTP as HTTPS is not supported.
    • For the S3 bucket, the default Origin protocol policy is Match Viewer and cannot be changed. So When CloudFront is configured to require HTTPS between the viewer and CloudFront, it automatically uses HTTPS to communicate with S3.

HTTPS Connection

  • CloudFront can also be configured to work with HTTPS for alternate domain names by using:-
    • Serving HTTPS Requests Using Dedicated IP Addresses
      • CloudFront associates the alternate domain name with a dedicated IP address, and the certificate is associated with the IP address when a request is received from a DNS server for the IP address.
      • CloudFront uses the IP address to identify the distribution and the SSL/TLS certificate to return to the viewer.
      • This method works for every HTTPS request, regardless of the browser or other viewer that the user is using.
      • An additional monthly charge (of about $600/month) is incurred for using a dedicated IP address.
    • Serving HTTPS Requests Using Server Name Indication – SNI
      • SNI Custom SSL relies on the SNI extension of the TLS protocol, which allows multiple domains to be served over the same IP address by including the hostname, viewers are trying to connect to
      • With the SNI method, CloudFront associates an IP address with the alternate domain name, but the IP address is not dedicated.
      • CloudFront can’t determine, based on the IP address, which domain the request is for as the IP address is not dedicated.
      • Browsers that support SNI automatically get the domain name from the request URL & add it to a new field in the request header.
      • When CloudFront receives an HTTPS request from a browser that supports SNI, it finds the domain name in the request header and responds to the request with the applicable SSL/TLS certificate.
      • Viewer and CloudFront perform SSL negotiation, and CloudFront returns the requested content to the viewer.
      • Older browsers do not support SNI.
      • SNI Custom SSL is available at no additional cost beyond standard CloudFront data transfer and request fees
    • For End-to-End HTTPS connections certificate needs to be applied both between the Viewers and CloudFront & CloudFront and Origin, with the following requirements
      • HTTPS between viewers and CloudFront
        • A certificate that was issued by a trusted certificate authority (CA) such as Comodo, DigiCert, or Symantec;
        • Certificate provided by AWS Certificate Manager (ACM);
        • self-signed certificate
      • HTTPS between CloudFront and the Custom Origin
        • If the origin is not an ELB load balancer, the certificate must be issued by a trusted CA such as Comodo, DigiCert, or Symantec.
        • For load balancer, a certificate provided by ACM can be used
        • Self-signed certificates CAN NOT be used.
      • ACM certificate for CloudFront must be requested or imported in the US East (N. Virginia) region. ACM certificates in this region that are associated with a CloudFront distribution are distributed to all the geographic locations configured for that distribution.

Allowed HTTP methods

  • CloudFront supports GET, HEAD, OPTIONS, PUT, POST, PATCH, DELETE to get, add, update, and delete objects, and to get object headers.
    • GET, HEAD methods to use to get objects, object headers
    • GET, HEAD, OPTIONS methods to use to get objects, object headers or retrieve a list of the options supported from the origin
    • GET, HEAD, OPTIONS, PUT, POST, PATCH, DELETE operations can also be performed for e.g. submitting data from a web form, which are directly proxied back to the Origin server
  • CloudFront only caches responses to GET and HEAD requests and, optionally, OPTIONS requests. CloudFront does not cache responses to PUT, POST, PATCH, DELETE request methods and these requests are directed to the origin.
  • PUT, POST HTTP methods also help for accelerated content uploads, as these operations will be sent to the origin e.g. S3 via the CloudFront edge location, improving efficiency, reducing latency, and allowing the application to benefit from the monitored, persistent connections that CloudFront maintains from the edge locations to the origin servers.

CloudFront Edge Caches

  • Control the cache max-age
    • To increase the cache hit ratio, the origin can be configured to add a Cache-Control: max-age  directive to the objects.
    • Longer the interval less frequently it would be retrieved from the origin
  • Caching Based on Query String Parameters
    • CloudFront can be configured to cache based on the query parameters
      • None (Improves Caching) – if the origin returns the same version of an object regardless of the values of query string parameters.
      • Forward all, cache based on whitelist – if the origin server returns different versions of the objects based on one or more query string parameters. Then specify the parameters that you want CloudFront to use as a basis for caching in the Query String Whitelist field.
      • Forward all, cache based on all – if the origin server returns different versions of the objects for all query string parameters.
    • Caching performance can be improved by
      • Configure CloudFront to forward only the query strings for which the origin will return unique objects.
      • Using the same case for the parameters’ values for e.g. parameter value A or a, CloudFront would cache the same request twice even if the response or object returned is identical
      • Using the same parameter order for e.g. for request a=x&b=y and b=y&a=x, CloudFront would cache the same request twice even though the response or object returned is identical
    • For RTMP distributions, when CloudFront requests an object from the origin server, it removes any query string parameters.
  • Caching Based on Cookie Values
    • CloudFront can be configured to cache based on cookie values.
    • By default, it doesn’t consider cookies while caching on edge locations
    • Caching performance can be improved by
      • Configure CloudFront to forward only specified cookies instead of forwarding all cookies for e.g. if the request has 2 cookies with 3 possible values, CloudFront would cache all possible combinations even if the response takes into account a single cookie
      • Cookie names and values are both case sensitive so better to stick with the same case
      • Create separate cache behaviors for static and dynamic content, and configure CloudFront to forward cookies to the origin only for dynamic content for e.g. for CSS files, the cookies do not make sense as the object does not change with the cookie value
      • If possible, create separate cache behaviors for dynamic content for which cookie values are unique for each user (such as a user ID) and dynamic content that varies based on a smaller number of unique values reducing the number of combinations
    • For RTMP distributions, CloudFront cannot be configured to process
      cookies. When CloudFront requests an object from the origin server, it removes any cookies before forwarding the request to your origin. If your origin returns any cookies along with the object, CloudFront
      removes them before returning the object to the viewer.
  • Caching Based on Request Headers
    • CloudFront can be configured to cache based on request headers
    • By default, CloudFront doesn’t consider headers when caching the objects in edge locations.
    • CloudFront configured to cache based on request headers, does not change the headers that CloudFront forwards, only whether CloudFront caches objects based on the header values.
    • Caching performance can be improved by
      • Configure CloudFront to forward and cache based only on specified headers instead of forwarding and caching based on all headers.
      • Try to avoid caching based on request headers that have large numbers of unique values.
      • CloudFront is configured to forward all headers to the origin, CloudFront doesn’t cache the objects associated with this cache behaviour. Instead, it sends every request to the origin
      • CloudFront caches based on header values, it doesn’t consider the case of the header name but considers the case of the header value
    • For RTMP distributions, CloudFront cannot be configured to cache based on header values.

Object Caching & Expiration

  • Object expiration determines how long the objects stay in a CloudFront cache before it fetches it again from Origin.
  • Low expiration time helps serve content that changes frequently and high expiration time helps improve performance and reduce the origin load.
  • By default, each object automatically expires after 24 hours
  • After expiration time, CloudFront checks if it still has the latest version
    • If the cache already has the latest version, the origin returns a 304 status code (Not Modified).
    • If the CloudFront cache does not have the latest version, the origin returns a 200 status code (OK), and the latest version of the object
  • If an object in an edge location isn’t frequently requested, CloudFront might evict the object, and remove the object before its expiration date to make room for objects that have been requested more recently.
  • For Web distributions, the default behaviour can be changed by
    • for the entire path pattern, cache behaviour can be configured by the setting Minimum TTL, Maximum TTL, and Default TTL values
    • for individual objects, the origin can be configured to add a Cache-Control max-age or Cache-Control s-maxage directive, or an Expires header field to the object.
    • AWS recommends using Cache-Control max-age directive over Expires header to control object caching behaviour.
    • CloudFront uses only the value of Cache-Control max-age , if both the Cache-Control max-age directive and Expires header is specified
    • HTTP Cache-Control or Pragma header fields in a GET request from a viewer can’t be used to force CloudFront to go back to the origin server for the object
    • By default, when the origin returns an HTTP 4xx or 5xx status code, CloudFront caches these error responses for five minutes and then submit the next request for the object to the origin to see whether
      the requested object is available and the problem has been resolved
  • For RTMP distributions
    • Cache-Control or Expires headers can be added to objects to change the amount of time that CloudFront keeps objects in edge caches before it forwards another request to the origin.
    • Minimum duration is 3600 seconds (one hour). If you specify a lower value, CloudFront uses 3600 seconds.

CloudFront Origin Shield

  • CloudFront Origin Shield provides an additional layer in the CloudFront caching infrastructure that helps to minimize the origin’s load, improve its availability, and reduce its operating costs.
  • Origin Shield provides a centralized caching layer that helps increase the cache hit ratio to reduce the load on your origin.
  • Origin Shield decreases the origin operating costs by collapsing requests across regions so as few as one request goes to the origin per object.
  • Origin Shield can be configured by choosing the Regional Edge Cache closest to the origin to become the Origin Shield Region
  • CloudFront Origin Shield is beneficial for many use cases like
    • Viewers that are spread across different geographical regions
    • Origins that provide just-in-time packaging for live streaming or on-the-fly image processing
    • On-premises origins with capacity or bandwidth constraints
    • Workloads that use multiple content delivery networks (CDNs)

Serving Compressed Files

  • CloudFront can be configured to automatically compress files of certain types and serve the compressed files when viewer requests include Accept-Encoding in the request header
  • Compressing content, downloads are faster because the files are smaller as well as less expensive as the cost of CloudFront data transfer is based on the total amount of data served.
  • CloudFront can compress objects using the Gzip and Brotli compression formats.
  • If serving from a custom origin, it can be used to
    • configure to compress files with or without CloudFront compression
    • compress file types that CloudFront doesn’t compress.
  • If the origin returns a compressed file, CloudFront detects compression by the Content-Encoding header value and doesn’t compress the file again.
  • CloudFront serves content using compression as below
    1. CloudFront distribution is created and configured to compress content.
    2. A viewer requests a compressed file by adding the Accept-Encoding header with includes gzipbr, or both to the request.
    3. At the edge location, CloudFront checks the cache for a compressed version of the file that is referenced in the request.
    4. If the compressed file is already in the cache, CloudFront returns the file to the viewer and skips the remaining steps.
    5. If the compressed file is not in the cache, CloudFront forwards the request to the origin server (S3 bucket or a custom origin)
    6. Even if CloudFront has an uncompressed version of the file in the cache, it still forwards a request to the origin.
    7. Origin server returns an uncompressed version of the requested file
    8. CloudFront determines whether the file is compressible:
      1. file must be of a type that CloudFront compresses.
      2. file size must be between 1,000 and 10,000,000 bytes.
      3. response must include a Content-Length header to determine the size within valid compression limits. If the Content-Length header is missing, CloudFront won’t compress the file.
      4. value of the Content-Encoding header on the file must not be gzip i.e. the origin has already compressed the file.
      5. the response should have a body.
      6. response HTTP status code should be 200, 403, or 404
    9. If the file is compressible, CloudFront compresses it, returns the compressed file to the viewer, and adds it to the cache.
    10. The viewer uncompresses the file.

Distribution Details

Price Class

  • CloudFront has edge locations all over the world and the cost for each edge location varies and the price charged for serving the requests also varies
  • CloudFront edge locations are grouped into geographic regions, and regions have been grouped into price classes
    • Price Class – includes all the regions
    • Another price class includes most regions (the United States; Europe; Hong Kong, Korea, and Singapore; Japan; and India regions) but excludes the most expensive regions
    • Price Class 200 – Includes All regions except South America and Australia and New Zealand.
    • Price Class 100 – A third price class includes only the least-expensive regions (North America and Europe regions)
  • Price class can be selected to lower the cost but this would come only at the expense of performance (higher latency), as CloudFront would serve requests only from the selected price class edge locations
  • CloudFront may, sometimes, service requests from a region not included within the price class, however, you would be charged the rate for the least-expensive region in your selected price class

WAF Web ACL

  • AWS WAF can be used to allow or block requests based on specified criteria, choose the web ACL to associate with this distribution.

Alternate Domain Names (CNAMEs)

  • CloudFront by default assigns a domain name for the distribution for e.g. d111111abcdef8.cloudfront.net
  • An alternate domain name, also known as a CNAME, can be used to use own custom domain name for links to objects
  • Both web and RTMP distributions support alternate domain names.
  • CloudFront supports * wildcard at the beginning of a domain name instead of specifying subdomains individually.
  • However, a wildcard cannot replace part of a subdomain name for e.g. *domain.example.com, or cannot replace a subdomain in the middle of a domain name for e.g. subdomain.*.example.com.

Distribution State

  • Distribution state indicates whether you want the distribution to be enabled or disabled once it’s deployed.

Geo-Restriction – Geoblocking

  • Geo restriction can help allow or prevent users in selected countries from accessing the content,
  • CloudFront distribution can be configured either to allow users in
    • whitelist of specified countries to access the content or to
    • deny users in a blacklist of specified countries to access the content
  • Geo restriction can be used to restrict access to all of the files that are
    associated with distribution and to restrict access at the country level
  • CloudFront responds to a request from a viewer in a restricted country with an HTTP status code 403 (Forbidden)
  • Use a third-party geolocation service, if access is to be restricted to a subset of the files that are associated with a distribution or to restrict access at a finer granularity than the country level.

CloudFront Edge Functions

Refer blog post @ CloudFront Edge Functions

CloudFront with S3

AWS CloudFront with S3

CloudFront Security

  • CloudFront provides Encryption in Transit and can be configured to require that viewers use HTTPS to request the files so that connections are encrypted when CloudFront communicates with viewers.
  • CloudFront provides Encryption at Rest
    • uses SSDs which are encrypted for edge location points of presence (POPs), and encrypted EBS volumes for Regional Edge Caches (RECs).
    • Function code and configuration are always stored in an encrypted format on the encrypted SSDs on the edge location POPs, and in other storage locations used by CloudFront.
  • Restricting access to content
    • Configure HTTPS connections
    • Use signed URLs or cookies to restrict access for selected users
    • Restrict access to content in S3 buckets using origin access identity – OAI, to prevent users from using the direct URL of the file.
    • Set up field-level encryption for specific content fields
    • Use AWS WAF web ACLs to create a web access control list (web ACL) to restrict access to your content.
    • Use geo-restriction, also known as geoblocking, to prevent users in specific geographic locations from accessing content served through a CloudFront distribution.

AWS CloudFront Security

Access Logs

  • CloudFront can be configured to create log files that contain detailed information about every user request that CloudFront receives.
  • Access logs are available for both web and RTMP distributions.
  • With logging enabled, an S3 bucket can be specified where CloudFront would save the files
  • CloudFront delivers access logs for a distribution periodically, up to several times an hour
  • CloudFront usually delivers the log file for that time period to the S3 bucket within an hour of the events that appear in the log. Note, however, that some or all log file entries for a time period can sometimes be delayed by up to 24 hours

CloudFront Cost

  • CloudFront charges are based on actual usage of the service in four areas:
    • Data Transfer Out to Internet
      • charges are applied for the volume of data transferred out of the CloudFront edge locations, measured in GB
      • Data transfer out from AWS origin (e.g., S3, EC2, etc.) to CloudFront are no longer charged. This applies to data transfer from all AWS regions to all global CloudFront edge locations
    • HTTP/HTTPS Requests
      • number of HTTP/HTTPS requests made for the content
    • Invalidation Requests
      • per path in the invalidation request
      • A path listed in the invalidation request represents the URL (or multiple URLs if the path contains a wildcard character) of the object you want to invalidate from the CloudFront cache
    • Dedicated IP Custom SSL certificates associated with a CloudFront distribution
      • $600 per month for each custom SSL certificate associated with one or more CloudFront distributions using the Dedicated IP version of custom SSL certificate support, pro-rated by the hour

CloudFront vs Global Accelerator

Refer blog post @ CloudFront vs Global Accelerator

AWS Certification Exam Practice Questions

  • Questions are collected from Internet and the answers are marked as per my knowledge and understanding (which might differ with yours).
  • AWS services are updated everyday and both the answers and questions might be outdated soon, so research accordingly.
  • AWS exam questions are not updated to keep up the pace with AWS updates, so even if the underlying feature has changed the question might not be updated
  • Open to further feedback, discussion and correction.
  1. Your company Is moving towards tracking web page users with a small tracking Image loaded on each page Currently you are serving this image out of US-East, but are starting to get concerned about the time It takes to load the image for users on the west coast. What are the two best ways to speed up serving this image? Choose 2 answers
    1. Use Route 53’s Latency Based Routing and serve the image out of US-West-2 as well as US-East-1
    2. Serve the image out through CloudFront
    3. Serve the image out of S3 so that it isn’t being served oft of your web application tier
    4. Use EBS PIOPs to serve the image faster out of your EC2 instances
  2. You deployed your company website using Elastic Beanstalk and you enabled log file rotation to S3. An Elastic Map Reduce job is periodically analyzing the logs on S3 to build a usage dashboard that you share with your CIO. You recently improved overall performance of the website using Cloud Front for dynamic content delivery and your website as the origin. After this architectural change, the usage dashboard shows that the traffic on your website dropped by an order of magnitude. How do you fix your usage dashboard’? [PROFESSIONAL]
    1. Enable CloudFront to deliver access logs to S3 and use them as input of the Elastic Map Reduce job
    2. Turn on Cloud Trail and use trail log tiles on S3 as input of the Elastic Map Reduce job
    3. Change your log collection process to use Cloud Watch ELB metrics as input of the Elastic Map Reduce job
    4. Use Elastic Beanstalk “Rebuild Environment” option to update log delivery to the Elastic Map Reduce job.
    5. Use Elastic Beanstalk ‘Restart App server(s)” option to update log delivery to the Elastic Map Reduce job.
  3. An AWS customer runs a public blogging website. The site users upload two million blog entries a month. The average blog entry size is 200 KB. The access rate to blog entries drops to negligible 6 months after publication and users rarely access a blog entry 1 year after publication. Additionally, blog entries have a high update rate during the first 3 months following publication; this drops to no updates after 6 months. The customer wants to use CloudFront to improve his user’s load times. Which of the following recommendations would you make to the customer? [PROFESSIONAL]
    1. Duplicate entries into two different buckets and create two separate CloudFront distributions where S3 access is restricted only to Cloud Front identity
    2. Create a CloudFront distribution with “US & Europe” price class for US/Europe users and a different CloudFront distribution with All Edge Locations for the remaining users.
    3. Create a CloudFront distribution with S3 access restricted only to the CloudFront identity and partition the blog entry’s location in S3 according to the month it was uploaded to be used with CloudFront behaviors
    4. Create a CloudFront distribution with Restrict Viewer Access Forward Query string set to true and minimum TTL of 0.
  4. Your company has on-premises multi-tier PHP web application, which recently experienced downtime due to a large burst in web traffic due to a company announcement. Over the coming days, you are expecting similar announcements to drive similar unpredictable bursts, and are looking to find ways to quickly improve your infrastructures ability to handle unexpected increases in traffic. The application currently consists of 2 tiers a web tier, which consists of a load balancer, and several Linux Apache web servers as well as a database tier which hosts a Linux server hosting a MySQL database. Which scenario below will provide full site functionality, while helping to improve the ability of your application in the short timeframe required? [PROFESSIONAL]
    1. Offload traffic from on-premises environment Setup a CloudFront distribution and configure CloudFront to cache objects from a custom origin Choose to customize your object cache behavior, and select a TTL that objects should exist in cache.
    2. Migrate to AWS Use VM Import/Export to quickly convert an on-premises web server to an AMI create an Auto Scaling group, which uses the imported AMI to scale the web tier based on incoming traffic Create an RDS read replica and setup replication between the RDS instance and on-premises MySQL server to migrate the database.
    3. Failover environment: Create an S3 bucket and configure it tor website hosting Migrate your DNS to Route53 using zone (lie import and leverage Route53 DNS failover to failover to the S3 hosted website.
    4. Hybrid environment Create an AMI which can be used of launch web serfers in EC2 Create an Auto Scaling group which uses the * AMI to scale the web tier based on incoming traffic Leverage Elastic Load Balancing to balance traffic between on-premises web servers and those hosted in AWS.
  5. You are building a system to distribute confidential training videos to employees. Using CloudFront, what method could be used to serve content that is stored in S3, but not publically accessible from S3 directly?
    1. Create an Origin Access Identity (OAI) for CloudFront and grant access to the objects in your S3 bucket to that OAI.
    2. Add the CloudFront account security group “amazon-cf/amazon-cf-sg” to the appropriate S3 bucket policy.
    3. Create an Identity and Access Management (IAM) User for CloudFront and grant access to the objects in your S3 bucket to that IAM User.
    4. Create a S3 bucket policy that lists the CloudFront distribution ID as the Principal and the target bucket as the Amazon Resource Name (ARN).
  6. A media production company wants to deliver high-definition raw video for preproduction and dubbing to customer all around the world. They would like to use Amazon CloudFront for their scenario, and they require the ability to limit downloads per customer and video file to a configurable number. A CloudFront download distribution with TTL=0 was already setup to make sure all client HTTP requests hit an authentication backend on Amazon Elastic Compute Cloud (EC2)/Amazon RDS first, which is responsible for restricting the number of downloads. Content is stored in S3 and configured to be accessible only via CloudFront. What else needs to be done to achieve an architecture that meets the requirements? Choose 2 answers [PROFESSIONAL]
    1. Enable URL parameter forwarding, let the authentication backend count the number of downloads per customer in RDS, and return the content S3 URL unless the download limit is reached.
    2. Enable CloudFront logging into an S3 bucket, leverage EMR to analyze CloudFront logs to determine the number of downloads per customer, and return the content S3 URL unless the download limit is reached. (CloudFront logs are logged periodically and EMR not being real time, hence not suitable)
    3. Enable URL parameter forwarding, let the authentication backend count the number of downloads per customer in RDS, and invalidate the CloudFront distribution as soon as the download limit is reached. (Distribution are not invalidated but Objects)
    4. Enable CloudFront logging into the S3 bucket, let the authentication backend determine the number of downloads per customer by parsing those logs, and return the content S3 URL unless the download limit is reached. (CloudFront logs are logged periodically and EMR not being real time, hence not suitable)
    5. Configure a list of trusted signers, let the authentication backend count the number of download requests per customer in RDS, and return a dynamically signed URL unless the download limit is reached.
  7. Your customer is implementing a video on-demand streaming platform on AWS. The requirements are to support for multiple devices such as iOS, Android, and PC as client devices, using a standard client player, using streaming technology (not download) and scalable architecture with cost effectiveness [PROFESSIONAL]
    1. Store the video contents to Amazon Simple Storage Service (S3) as an origin server. Configure the Amazon CloudFront distribution with a streaming option to stream the video contents
    2. Store the video contents to Amazon S3 as an origin server. Configure the Amazon CloudFront distribution with a download option to stream the video contents (Refer link)
    3. Launch a streaming server on Amazon Elastic Compute Cloud (EC2) (for example, Adobe Media Server), and store the video contents as an origin server. Configure the Amazon CloudFront distribution with a download option to stream the video contents
    4. Launch a streaming server on Amazon Elastic Compute Cloud (EC2) (for example, Adobe Media Server), and store the video contents as an origin server. Launch and configure the required amount of streaming servers on Amazon EC2 as an edge server to stream the video contents
  8. You are an architect for a news -sharing mobile application. Anywhere in the world, your users can see local news on of topics they choose. They can post pictures and videos from inside the application. Since the application is being used on a mobile phone, connection stability is required for uploading content, and delivery should be quick. Content is accessed a lot in the first minutes after it has been posted, but is quickly replaced by new content before disappearing. The local nature of the news means that 90 percent of the uploaded content is then read locally (less than a hundred kilometers from where it was posted). What solution will optimize the user experience when users upload and view content (by minimizing page load times and minimizing upload times)? [PROFESSIONAL]
    1. Upload and store the content in a central Amazon Simple Storage Service (S3) bucket, and use an Amazon Cloud Front Distribution for content delivery.
    2. Upload and store the content in an Amazon Simple Storage Service (S3) bucket in the region closest to the user, and use multiple Amazon Cloud Front distributions for content delivery.
    3. Upload the content to an Amazon Elastic Compute Cloud (EC2) instance in the region closest to the user, send the content to a central Amazon Simple Storage Service (S3) bucket, and use an Amazon Cloud Front distribution for content delivery.
    4. Use an Amazon Cloud Front distribution for uploading the content to a central Amazon Simple Storage Service (S3) bucket and for content delivery.
  9. To enable end-to-end HTTPS connections from the user‘s browser to the origin via CloudFront, which of the following options are valid? Choose 2 answers [PROFESSIONAL]
    1. Use self signed certificate in the origin and CloudFront default certificate in CloudFront. (Origin cannot be self signed)
    2. Use the CloudFront default certificate in both origin and CloudFront (CloudFront cert cannot be applied to origin)
    3. Use 3rd-party CA certificate in the origin and CloudFront default certificate in CloudFront
    4. Use 3rd-party CA certificate in both origin and CloudFront
    5. Use a self signed certificate in both the origin and CloudFront (Origin cannot be self signed)
  10. Your application consists of 10% writes and 90% reads. You currently service all requests through a Route53 Alias Record directed towards an AWS ELB, which sits in front of an EC2 Auto Scaling Group. Your system is getting very expensive when there are large traffic spikes during certain news events, during which many more people request to read similar data all at the same time. What is the simplest and cheapest way to reduce costs and scale with spikes like this? [PROFESSIONAL]
    1. Create an S3 bucket and asynchronously replicate common requests responses into S3 objects. When a request comes in for a precomputed response, redirect to AWS S3
    2. Create another ELB and Auto Scaling Group layer mounted on top of the other system, adding a tier to the system. Serve most read requests out of the top layer
    3. Create a CloudFront Distribution and direct Route53 to the Distribution. Use the ELB as an Origin and specify Cache Behaviors to proxy cache requests, which can be served late. (CloudFront can server request from cache and multiple cache behavior can be defined based on rules for a given URL pattern based on file extensions, file names, or any portion of a URL. Each cache behavior can include the CloudFront configuration values: origin server name, viewer connection protocol, minimum expiration period, query string parameters, cookies, and trusted signers for private content.)
    4. Create a Memcached cluster in AWS ElastiCache. Create cache logic to serve requests, which can be served late from the in-memory cache for increased performance.
  11. You are designing a service that aggregates clickstream data in batch and delivers reports to subscribers via email only once per week. Data is extremely spikey, geographically distributed, high-scale, and unpredictable. How should you design this system?
    1. Use a large RedShift cluster to perform the analysis, and a fleet of Lambdas to perform record inserts into the RedShift tables. Lambda will scale rapidly enough for the traffic spikes.
    2. Use a CloudFront distribution with access log delivery to S3. Clicks should be recorded as query string GETs to the distribution. Reports are built and sent by periodically running EMR jobs over the access logs in S3. (CloudFront is a Gigabit-Scale HTTP(S) global request distribution service and works fine with peaks higher than 10 Gbps or 15,000 RPS. It can handle scale, geo-spread, spikes, and unpredictability. Access Logs will contain the GET data and work just fine for batch analysis and email using EMR. Other streaming options are expensive as not required as the need is to batch analyze)
    3. Use API Gateway invoking Lambdas which PutRecords into Kinesis, and EMR running Spark performing GetRecords on Kinesis to scale with spikes. Spark on EMR outputs the analysis to S3, which are sent out via email.
    4. Use AWS Elasticsearch service and EC2 Auto Scaling groups. The Autoscaling groups scale based on click throughput and stream into the Elasticsearch domain, which is also scalable. Use Kibana to generate reports periodically.
  12. Your website is serving on-demand training videos to your workforce. Videos are uploaded monthly in high resolution MP4 format. Your workforce is distributed globally often on the move and using company-provided tablets that require the HTTP Live Streaming (HLS) protocol to watch a video. Your company has no video transcoding expertise and it required you might need to pay for a consultant. How do you implement the most cost-efficient architecture without compromising high availability and quality of video delivery? [PROFESSIONAL]
    1. Elastic Transcoder to transcode original high-resolution MP4 videos to HLS. S3 to host videos with lifecycle Management to archive original flies to Glacier after a few days. CloudFront to serve HLS transcoded videos from S3
    2. A video transcoding pipeline running on EC2 using SQS to distribute tasks and Auto Scaling to adjust the number or nodes depending on the length of the queue S3 to host videos with Lifecycle Management to archive all files to Glacier after a few days CloudFront to serve HLS transcoding videos from Glacier
    3. Elastic Transcoder to transcode original high-resolution MP4 videos to HLS EBS volumes to host videos and EBS snapshots to incrementally backup original rues after a few days. CloudFront to serve HLS transcoded videos from EC2.
    4. A video transcoding pipeline running on EC2 using SQS to distribute tasks and Auto Scaling to adjust the number of nodes depending on the length of the queue. EBS volumes to host videos and EBS snapshots to incrementally backup original files after a few days. CloudFront to serve HLS transcoded videos from EC2

References