Section - Caching

Question 1

What is Amazon CloudFront?

Answer 1

CloudFront is a CDN that delivers data and applications globally with low latency.

• Makes content available globally or restricts it based on location
• Speeds up delivery of static and dynamic web content
• CloudFront Edge Locations to cache content, separate to an AWS Region/AZ
• CloutFront Origin is the origin of all the files that the distribution will serve. Can be S3 Bucket, an EC2 Instance, an Elastic Load Balancer, or Route53
• Defaults to HTTPS connections with the ability to add custom SSL certificate.
• You can’t pick specific countries, just general areas of the globe (e.g. continents)
• Supports both AWS endpoints as well as non-AWS applications
• CloudFront Distribution is the name given to the Origin and configuration settings for the content you wish to distribute using CloudFront(CDN)
• Objects are cached for a period of time which is their Time To Live(TTL).
  
  • The default TTL is 1 day, and when the TTL is up, the object is automatically cleared from cache.
  • You can clear an object from the cache yourself before the TTL is up, but you will be charged.

NB:
Did you know that if the content is already in the edge location, CloudFront delivers it immediately? If not, CloudFront retrieves the files from the origin.

Question 2

How to use Amazon CloudFront in the Real world?

Answer 2

• CloudFront is used with S3 to deploy content (Static Website)
• CloudFronT can stop certain web attacks like DDoS.
• Geo-restricition prevents users in certain countries from accessing content.

Question 3

What is Amazon Global Accelerator?

Answer 3

Global Accelerator sends your users through the AWS global network when accessing your content, speeding up delivery.

• Improves latency and availability of single-Region applications
• Sends traffic through the AWS global network infrastructure
• 60% performance boost
• Automatically re-routes traffic to healthy available regional endpoints

NB: Exam Scenario talks about IP Caching, use Global Accelerator

Question 4

What is Amazon S3 Transfer Acceleration?

Answer 4

S3 Transfer Acceleration improves content uploads and downloads to and from S3 buckets.

• Fast transfer of files over long distances
• Uses CloudFront’s globally distributed edge locations
• Customers around the world can upload to a central bucket

Question 5

AWS DynamoDB Accelerator (DAX)?

Answer 5

• DynamoDB Accelerator (Or DAX) is a fully managed, clustered in-memory cache for DynamoDB
• Delivers up to a 10x read performance improvement. Microsecond performance for millions of requests per second.
• DAX is a write-through caching service. Data is written to the cache and the backend store at the same time.
• DynamoDB API calls are pointed to DAX (cache), and if an item is not found then DAX gets the item from the DynamoDB, caches it and send it back to the API call.
• Caters for eventually consistent reads only.
• No suitable for:
  
  • Applications which are mainly write intensive
  • Applications that do not perform many read operations
• Ideal for:
  
  • Read-heavy workloads and bursty wordloads
  • e.g. Auction applications,Gaming site, Ecommerce (Black Friday sale)

Question 6

What is Amazon ElastiCache?

Answer 6

ElastiCache is a fully managed in-memory datastore compatible with Redis or Memcached.

• In-memory datastore
• Compatible with Redis or Memcached engines
• Data can be lost
• Offers high performance and low latency

Question 7

Two types of ElastiCache?

Answer 7

Memcached:

• Great for basic object caching
• Scales horizontally, but there is no persistance, no Multi-AZ or failover.
• a good choice if you want basic caching and you want your caching model to be as simple as possible.

Redis:

• A more sophisticated solution enterprise features like persistance, replication, Multi-AZ and failover.
• Supports sorting and ranking data (e.g. for gaming leaderboards), and complex data types like lists and hashes.
• Also supports backups

Question 8

ElasticCache scenarios?

Answer 8

• Database under stress:
  
  • heavy reads
  • data does not change frequently