Scaled Web Service

Design of a system that supports a million users.

In the diagram below there is:

• Servers in multiple DataCentres (AvailabilityZone) for redundancy
• An ELB load-balances web traffic between Ec2 instances in an AutoScalingGroup.
  • This is an instance of HorizontalScaling (as opposed to VerticalScaling)
• The Ec2 instances are Stateless.
  • State is stored in a NonRelational database e.g. DynamoDB.
  • Data is stored in an Rds making use of RDSMultiAz i.e. a database with MasterSlaveReplication. To scale further consider Sharding.
• To improve performance to the Rds databases Caching is used.
• A MessageQueues (SQS) is used for doing expensive calculations asynchronously using Lambda.
• CloudWatch is used to monitor the system.
• A CDN (CloudFront) is used to host static assets.