Scaling Architecture

Question 1

Describe the features of Horizontal Scaling

Answer 1

• Add more instances as demand increases
• No downtime required to scale in/out
• Automatic using ASG’s
• Theoretically unlimited

Question 2

Describe the features of Vertical Scaling

Answer 2

• Add more CPU/Mem to existing instances
• Requires restart to scale
• Requires scripting to automate
• Limited by instance size

Question 3

Describe EC2 Auto-Scaling

Answer 3

Focused on EC2 instances, uses scaling groups and health checks to manage

Question 4

Describe App Auto-Scaling

Answer 4

For scaling resources other than EC2 (dynamodb, ECS, EMR, etc).

Question 5

Describe AWS Auto-scaling

Answer 5

Centralised way to manage EC2 and App Autoscaling features

Question 6

Describe the 3 Scaling Policies

Answer 6

Target Tracking - Scale based on set metrics (eg: scale if EC2’s are above 70% CPU usage

Simple Scaling - Wait til health check and cooldown periods expire before evaluating need for scaling (eg: increase spot fleet by 20% per 10K connections to the ELB)

Step Scaling - Scale with advanced logic

Question 7

Describe Scaling cooldown

Answer 7

Giving resources x time to get ready and absorb load before health checks apply. Auto applies to dynamic scaling, optional for Manual scaling. Defaults to 300sec

Question 8

Describe Kinesis Data Streams

Answer 8

Stream information between client devices and app servers/services (think EC2, Lambda, Data Analytics tools, etc)

Question 9

Describe Kinesis Firehose

Answer 9

A data transfer service for sending data to storage services like S3, Elasticache, RDS, etc

Question 10

Describe Kinesis Shards and Records

Answer 10

A Shard is a individual package of data Records that Kinesis streams. Records each contain a Partition Key, Sequence Number, and Data Blob. Each Shard can ingest 1K records/sec.

Question 11

How does DynamoDB Scaling work

Answer 11

DynamoDB scales using partitions. Each scaling level adds a new Partition. Partitions can handle either 1000 Read Capacity Units RCU’s, or Write capacity Units WCU’s, each has 10GB of storage. Scaling occures when certain RCU or WCU limits are reached. Autoscaling is cheaper but harder to implement. On-demand scaling is more expensive.

Question 12

Does Cloudfront support Static or Dynamic content

Answer 12

It supports both

Question 13

Describe Standard vs FIFO Queues/Topics

Answer 13

Used in SQS and SNS. Standard is suitable if the order of messages doesn’t matter, and the app receiving the message can handle duplicates. FIFO ensures that messages are delivered in the order they’re received, and only sent once, which prevents duplicate message recipes.

Question 14

What’s the difference between SNS and SQS

Answer 14

SNS sends out messages, clients subscribe to a topic. SQS holds messages, clients request messages from a queue.

Question 15

What languages does LAMBDA support

Answer 15

Java, Go, PowerShell, Node. js, C#, Python, and Ruby

Question 16

What are Step Functions

Answer 16

A way to manage workflow in serverless apps

Question 17

What is AWS Batch

Answer 17

Cron jobs as a service, uses EC2 on the backend to provision workers to perform batch actions

Question 18

Describe loosely coupled architecture

Answer 18

Architecture that’s split into many discrete services with abstraction between them. More individual components that can be scaled independently.