AWS Certified Solutions Architect - Note (8)

Simple Queue Service (SQS)

SQS - Use Case

SQS Limits - Message Size

SQS Limits - Message Retention

SQS - Standard Queues

SQS - FIFO Queues

SQS - Visibility Timeout

SQS - Short vs Long Polling

SQS CheatSheet

  • SQS is a queuing service using messages with a queue. Think Sidekiq or RabbitMQ.
  • SQS is used for Application Integration, it lets decoupled services and apps to talk to each other.
  • To read SQS use need to pull the queue using the AWS SDK. SQS is not pushed-based.
  • SQS supports both Standard and First-ln-First-Out (FIFO) queues.
  • Standard allows nearly unlimited messages per second, does not guarantee order of delivery, always delivers at least once, you must protect again duplicate messages being processed.
  • FIFO maintain the order of messages with a 300 limit.
  • There are two kinds of polling Short (Default) and Long Polling.
  • Short polling returns messages immediately, even if the message queue being polled is empty.
  • Long polling waits until message arrives in the queue, or the long poll timeout expires.
  • In majority of cases Long polling is preferred over short polling.
  • Visibility time-out is the period of time that messages are invisible in the SQS queue.
  • Messages will be deleted from queue after a job has processed. (before visibility timeout expires)
  • If Visibility timeout expires than a job will become visible to the queue.
  • The default Visibility time-out is 30 seconds. Timeout can be 0 seconds to a maximum of 12 hours.
  • SQS can retain messages from 60 seconds to 14 days and by default is 4 days.
  • Message size between 1 byte to 256 kb, Extended Client Library for Java can increase to 2GB.

Simple Notification Service (SNS)

SNS - Topics

SNS - Subscriptions

Application As Subscriber

SNS CheatSheet

  • Simple Notification Service (SNS) is a fully managed pub/sub messaging service.
  • SNS is for Application Integration. It allows decoupled services and apps to communicate with each other.
  • Topic a logical access point and communication channel.
  • A topic is able to deliver to multiple protocols.
  • You can encrypt topics via KMS.
  • Publishers use the AWS API via AWS CLI or SDK to push messages to a topic. Many AWS services integrate with SNS and act as publishers.
  • Subscriptions subscribe to topics. When a topic receives a message it automatically and immediately pushes messages to subscribers.
  • All messages published to SNS are stored redundantly across multiple Availability Zones (AZ)
  • The following protocols:
    • HTTP and HTTPs create webhooks into your web-application.
    • Email good for internal email notifications (only supports plain text)
    • Email-JSON sends you json via email.
    • Amazon SQS place SNS message into SQS queue.
    • AWS Lambda triggers a lambda function.
    • SMS send a text message.
    • Platform application endpoints Mobile Push eg. Apple, Google, Microsoft Baidu notification systems.


ElastiCache - Caching Comparison

ElastiCache CheatSheet

  • ElastiCache is a managed in-memory caching service.
  • ElastiCache can launch either Memcached or Redis.
  • Memcached is a simple key / value store preferred for caching HTML fragments and is arguably faster than Redis.
  • Redis has richer data types and operations. Great for leaderboard, geospatial data or keeping track of unread notifications.
  • A cache is a temporary storage area.
  • Most frequently identical queries are stored in the cache.
  • Resources only within the same VPC may connect to ElastiCache to ensure low latencies.

High Availability(HA)

Scale Up vs Scale Out

Elastic Beanstalk

Elastic Beanstalk CheatSheet

  • Elastic Beanstalk handles the deployment, from capacity provisioning, load balancing, auto-scaling to application health monitoring.
  • When you want to run a web-application but you don’t want to have think about the underlying infrastructure.
  • It costs nothing to use Elastic Beanstalk (only the resources it provisions eg. RDS, ELB, EC2)
  • Recommended for test or development apps. Not recommended for production use.
  • You can choose from the following preconfigured platforms: Java, .NET, PHP, Node.js, Python, Ruby, Go, and Docker.
  • You can run dockerized environments on Elastic Beanstalk.
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