Classic Architecture Discussion

• This section discusses basic architectural solutions combining technical offerings provided by AWS

Stateless Web Apps: WhatIsTheTime.com

• WhatIsTheTime.com: allows people to know what time it is
• No database required
• We want to start small and can accept downtime at the beginning

• We want to be able to fully scale vertically and horizontally with no downtime

• Considerations when building the architecture:
  • Public IP vs private IP in case of EC2 instances
  • Elastic IP vs Route53 vs Load Balancers
  • Route53 TTL A records vs Alias Records
  • Maintaining EC2 instance scaling manually vs using an ASG
  • Multi AZ deployments to have disaster recovery
  • ELB Heath Checks
  • Security Groups Rules
  • Reservation of capacity for cost saving when possible
  • We are considering the 5 pillars of a well architected application: cost, performance, reliability, security and operational excellence

Stateful Web Apps: MyClothes.com

• MyClothes.com: allows people to buy clothes online
• There is a shopping cart for every user
• The application can have hundreds of users using the app in the same time
• We need to scale, maintain horizontal scalability and keep the app as stateless as possible
• Users should not loose their shopping cart while navigating the site

• Users should have their details in a database

• Consideration when building the architecture:
  • ELB sticky sessions
  • Web clients for storing cookies and making the application stateless
  • Session id + session cache which can be ElastiCache or DynamoDB
  • ElastiCache can be used to cache data from RDS
  • Multi AZ for disaster recovery
  • RDS:
    • We can use it for store user data
    • We can have read replicas for scaling reads
    • We can enable Multi AZ for disaster recovery
• Tight security using security groups

Instantiating Applications Quickly

• When launching a full stack application, it can take time to:
  • Install the application
  • Insert initial (or recovery) data
  • Configure everything
  • Launch the application
• In order to solve this we can use:
  • For EC2 Instances:
    • Golden AMI: install the application, OS, dependencies etc. beforehand and launch the EC2 instance from the Golden AMI
    • Bootstrap using User Data: for dynamic configuration we can use User Data scripts
  • For RDS databases we can restore the database from a snapshot
  • For EBS Volumes we can also restore the data from a snapshot