AWS SQS – Standard vs FIFO Queue – Certification

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AWS SQS – Standard vs FIFO Queue

SQS offers two types of queues – Standard & FIFO queues

SQS Standard vs FIFO

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


  • 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


  • Standard queues are available in all the regions
  • FIFO queues are currently available in limited regions including the US West (Oregon), US East (Ohio), US East (N. Virginia), and EU (Ireland)

SQS Buffered Asynchronous Client

  • FIFO queues aren’t currently compatible with the SQS Buffered Asynchronous Client, where messages are buffered at client side and send 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 scenarios, 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.

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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.

4 thoughts on “AWS SQS – Standard vs FIFO Queue – Certification

  1. Nice writeup, it looks identical to the write up amazon. Be original, please do not just cut and paste for the blog traffic. This speaks poorly of you

    1. Very much agreed. Some of the topics cannot have any added value cause they are short and concise already. I have included it for users to refer to directly on the blog linked with the preparation guide and practice questions. You are free to refer the original ones listed in the reference section.

  2. About this “Batch messages for future processing” ? I can’t find any documentation how it can be feasible. Do you know ?

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