• AWS Cloud Essentials Summary Part 2:
    • AWS has a global infrastructure to ensure high availability and low latency. 2 concepts to keep in mind:
      • Region: area where the AWS servers are located, isolated by default;
      • Availability Zones: there are 2 or 3 within each region and they rely on different infrastructures so they cannot get shut down contemporarily;
      • Edge Location: it uses CDN to cache copies locally when main server is far, can be handled with AWS Cloudfront;
    • How to choose a region?
      • Compliance requirements (if any);
      • Proximity to end customers;
      • Available features (for newest AWS services);
      • Pricing.
    • All resources are provisioned to API, there are several triggers:
      • Elastic Beanstalk and Cloud Formation are services used respectively for building the environment and automating it;
      • AWS CLI and SDK are used for scripting.
    • AWS VPC provisions resources privately but it has to be configured in subnets:
      • private subnets: resources within them cannot talk to the internet;
      • public subnets: resources within them can talk to the internet.
    • ACL are control lists are stateless and are like passport controls that check everyone who enters or exits a resource;
    • Security groups are stateful and are like doormen, they just check at the entrance and they remember you. Every EC2 instance has one;
    • The EC2 instances are ephemeral. and have cache that gets wiped out after shutting them down so data cannot be stored on them. Therefore, there are storage options:
      • EBS are volumes that are attached to an instance and provide storage. Great when a big file has to be edited, like a video or a photo. It is on Availability Zone level.;
      • S3 is a simple storage that has huge capacity, great for storing assets. It is serverless and regionally-distributed. Great when many files are fully-needed fast. According to the retrieval time, it has the “infrequent access” and “glacier” options: these are way cheaper than S3 standard so make sure to move items from standard to glacier when they are not trendy anymore;
      • EFS interacts with multiple EC2 instances and it’s on a regional level. More or less like EBS.

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