The AWS solutions architect certification shows that you can use AWS services to solve software engineering problems and understand core best practices of the industry. In this article, I will quiz you on two sections from the material required for the exam: CloudFront, ElastiCache.
I will now briefly state some key facts about each AWS service, and then provide some example questions for the exam.
N.B: The following information on its own will not be enough to answer the questions.
CloudFront
The CloudFront service is a global Content Delivery Network (CDN) service which allows users to distribute data with low latency and high transfer speeds.
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CloudFront Distribution Map — https://aws.amazon.com/cloudfront/features/*
It is also useful to know:
AWS CloudFront has 220+ Points of Presence (210+ Edge Locations and 12 Regional Edge Caches) in 87 cities across 44 countries.
Collections of files/sources are called Distributions.
Distributions can contain static files (HTML, JS, Audio, Video) and media streaming with valid origins of S3, EC2, ELB.
Distributions are accessed via a DNS name which can be ALIAS in Route53.
The CloudFront service uses DNS geo-location to serve content from closest edge location. If the content is not in the closest loation CloudFront fetches it from the origin server eg. S3.
The default cache expire time is 24hrs — this can be set using cache control headers or TTL.
Content can be evicted from an edge location (make room for more frequently requested content).
CloudFront offers an Invalidate API which enables users to invalidate based on patterns e.g.
*.html.Restrict access using signed urls, signed cookies, origin access Identities (OAI — special cloudfront users).
ElastiCache
The ElastiCache service is a managed scalable cache using the Memcached or Redis engines.
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Example ElastiCache Redis Cluster Architecture from https://www.iteanz.com/tutorials/aws/amazon-elasticache/*
It is also useful to know:
Memcached clusters can contain up to 20 nodes and perform auto discovery meaning there is no need to describe the topology in infrastructure.
A Redis cluster always contains a single node — clusters can be grouped in Redis replication group with a max of 5 read replicas.
ElastiCache is able to detect node failure and provision replacements in the cluster. There is a heavy load on your DB while the queries are performed to refill the cache.
If Redis Multi-AZ replication group is enabled a Read-Replica can be automatically promoted to being a primary node. Read replication is asynchronous.
Vertical Scaling an ElastiCache cluster requires users to spin up a new cluster of different instance size and redirect traffic.
A Redis snapshot is a full clone of data at a certain point of time and can be stored on S3.
Access to ElastiCache cluster can be deployed into VPC and access controlled with security groups.
Quiz 🎓
The quiz can also be accessed in full size here. These questions were sourced from multiple locations (mainly the certification sample test) over a long period of time.
Thanks For Reading
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