AWS SQS Standard vs FIFO Queue

SQS offers two types of queues – Standard & FIFO queues

SQS Standard vs FIFO Queue Features

Message Order

• Standard queues provide best-effort ordering which ensures that messages are generally delivered in the same order as they are sent. Occasionally (because of the highly-distributed architecture that allows high throughput), more than one copy of a message might be delivered out of order
• FIFO queues offer first-in-first-out delivery and exactly-once processing: the order in which messages are sent and received is strictly preserved

Delivery

• Standard queues guarantee that a message is delivered at least once and duplicates can be introduced into the queue
• FIFO queues ensure a message is delivered exactly once and remains available until a consumer processes and deletes it; duplicates are not introduced into the queue

Transactions Per Second (TPS)

• Standard queues allow nearly-unlimited number of transactions per second
• FIFO queues are limited to 300 transactions per second per API action. It can be increased to 3000 using batching.

Regions

• Standard & FIFO queues are now available in all the regions

SQS Buffered Asynchronous Client

• FIFO queues aren’t currently compatible with the SQS Buffered Asynchronous Client, where messages are buffered at the client side and sent as a single request to the SQS queue to reduce cost.

AWS Services Supported

• Standard Queues are supported by all AWS services
• FIFO Queues are currently not supported by all AWS services like
  • CloudWatch Events
  • S3 Event Notifications
  • SNS Topic Subscriptions
  • Auto Scaling Lifecycle Hooks
  • AWS IoT Rule Actions
  • AWS Lambda Dead Letter Queues

Use Cases

• Standard queues can be used in any scenario, as long as the application can process messages that arrive more than once and out of order
  • Decouple live user requests from intensive background work: Let users upload media while resizing or encoding it.
  • Allocate tasks to multiple worker nodes: Process a high number of credit card validation requests.
  • Batch messages for future processing: Schedule multiple entries to be added to a database.
• FIFO queues are designed to enhance messaging between applications when the order of operations and events is critical, or where duplicates can’t be tolerated
  • Ensure that user-entered commands are executed in the right order.
  • Display the correct product price by sending price modifications in the right order.
  • Prevent a student from enrolling in a course before registering for an account.

AWS Certification Exam Practice Questions

• Questions are collected from Internet and the answers are marked as per my knowledge and understanding (which might differ with yours).
• AWS services are updated everyday and both the answers and questions might be outdated soon, so research accordingly.
• AWS exam questions are not updated to keep up the pace with AWS updates, so even if the underlying feature has changed the question might not be updated
• Open to further feedback, discussion and correction.

1. A restaurant reservation application needs the ability to maintain a waiting list. When a customer tries to reserve a table, and none are available, the customer must be put on the waiting list, and the application must notify the customer when a table becomes free. What service should the Solutions Architect recommend ensuring that the system respects the order in which the customer requests are put onto the waiting list?
   1. Amazon SNS
   2. AWS Lambda with sequential dispatch
   3. A FIFO queue in Amazon SQS
   4. A standard queue in Amazon SQS
2. A solutions architect is designing an application for a two-step order process. The first step is synchronous and must return to the user with little latency. The second step takes longer, so it will be implemented in a separate component. Orders must be processed exactly once and in the order in which they are received. How should the solutions architect integrate these components?
   1. Use Amazon SQS FIFO queues.
   2. Use an AWS Lambda function along with Amazon SQS standard queues.
   3. Create an SNS topic and subscribe an Amazon SQS FIFO queue to that topic.
   4. Create an SNS topic and subscribe an Amazon SQS Standard queue to that topic.

References

AWS_SQS_Queue_Types