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Performant Architectures

Exam Questions

  • Elasticache -
  • Whenever they say "relational" - use RDS
  • Whenever they say "nosql" - DynamoDB
  • Whenever they say "data warehouse" - "Redshift!"
  • Not going to get tested on relational vs nonrelational
  • not an exam question, interview question!
  • 6 RDS Flavors - know them - look on the RDS homepage (mysql, postgres, etc)
  • Not going to get tested on using aurora vs rds choices
  • Do know what engines are supported
  • RDS: Which engines does RDS support read replica for?
  • Question: "offload main database because it's hit hard"
    • Use READ REPLICA
  • Question: "You need HA" and then multi AZ deployment
    • Use MULTI AZ DEPLOYMENT
  • Bring content closer to viewers and increase performance of website: CloudFront
  • Can cache dynamic or static content
  • Your clients are complaining that viewing your videos is really slow
  • Scale Out: I need better performance, should I increase the size of my instance or add a server?
  • The answer is ALWAYS add a server: scale out, add instances, use EC2 instance
  • Exam Question
  • Exam Anecdote: More exam questions about classic load balancer
  • Heard from 2 recent exam takers
  • Exam Question: Load Balancer checks health of ec2 instances behind load balancer
  • Question: "What happens then?"
    • Load balancer just stops routing requests until the instance is replaced or healthy
    • Auto scale manages health of the instance (replaces unhealthy instances with healthy instances)
  • Network Load Balancer: always use DNS name of load balancer, don't point your website at the load balancer IP address
  • EC2 Families: They might ask you what CPU instance type based on your needs

Topics

RDS

  • You pick a maintenance window and they apply the maintenance
  • Automated backups
  • Multi AZ deployments
  • Encryption at rest and in transit
  • Scalability: Read Replicas - same AZ or different AZ
  • Send some read requests there
  • Exam Question: Which engines does RDS support read replica for? All except oracle?

DynamoDB

  • key-value and document database
  • nosql
  • single-digit millisecond performance
  • multi-master available
  • now also available in aurora
  • multi-region available (up to you)
  • durable
  • RCU: Read Capacity Unit: One strongly consistent read per second OR 2 eventually consistent reads per second
  • Item up to 4kb in size
  • Need this for developer, I need so many reads/writes per second
  • WCU: Write Capacity Unit - item up to 1kb in size
  • 1 write per second

CloudFront

  • Fast CDN service
  • Dynamic or Static Content
  • Global Edge Network
  • Origins: S3, EC2, ELB, HTTP servers
  • Even if you have an on-prem HTTP server, you can still use cloudfront
  • Security: AWS Shield, AWS WAF (firewall)
  • Protect Private Content

Elasticache

memcached and redis - sysops and devops ask you to distinguish

One of these: memcached, redis

Scale Up

  • Increase size of hardware
  • more processing, more storage
  • Bigger EC2 instances

Scale Out

  • Adding more servers
  • Share the workload

  • Can be done on the flo

  • Scale Out: I need better performance, should I increase the size of my instance or add a server?

  • The answer is ALWAYS add a server: scale out, add instances, use EC2 instance
  • Trent: This goes into HA as well, instances can fail, we want to have a lot of instances
  • Trent: Probably save a lot of money scaling out with spot instances because they are so cheap, especially for http workers

Load Balancers

Exam Anecdote: More exam questions about classic load balancer

  • Classic Load Balancer
  • Layer 4 and Layer 7 (4 = transport layer, 7 = application layer)
  • Sticky sessions per user
  • Manages SSL - does all 4 protocols
  • Exam Question: Load Balancer checks health of ec2 instances behind load balancer
    • Question: "What happens then?"
    • Load balancer just stops routing requests until the instance is replaced or healthy
    • Auto scale manages health of the instance
  • Application Load Balancer
  • Layer 7 (application layer)
  • Route traffic to targets
  • only HTTP, HTTPS protocols support
  • Sysops & network certs
  • native ipv6
  • Target Groups: cannot assign instances, must make them a member of a target group
    • concept is specific to application load balancer, not done with classic load balancer
  • sticky sessions
  • advanced routing
  • Network Load Balancer
  • All about transport (layer 4)
  • Best performance load balancer
  • static IP support
    • Exam question: always use DNS name of load balancer, don't point your website at the load balancer IP address
  • TLS offloading
  • Supports SSL now

Auto Scaling

Better fault tolerance, better availability, better cost management

  • Cost Management
  • Elastic: Adjust number of instances
  • Health Check: terminate unhealthy instance and start a new one
  • Cattle vs Pets
  • Launch systems based on launch configuration
  • Scaling policy
  • if cpu > 95 add x instances
  • any other metric, whatever is good for application

EC2 Instance Types

  • Know the family and what they are for.
  • Exam Question EC2 Families: They might ask you what CPU instance type based on your needs
  • You don't need to know how many versions for each family, just know the family.

Some Handy mnemonics someone made up

  • T Family: general - burstable, good for dynamic workloads
  • M family: main for application - static, good for consistent workloads
  • C family: compute - good for small memory footprint and high compute
  • R family: RAM - high memory to CPU ratio
  • X family: extreme - high memory for CPU, general in-memory usage
  • P family: pictures - general graphics
  • F family: FPGA
  • G family: graphics intensive applications
  • H family: HDD backed
  • I family: SDD
  • D family: Dense - High disk ratio