Standard Queue vs FIFO Queue in AWS SQS: Key Differences and Usage

In AWS SQS, a Standard queue offers high throughput with at-least-once delivery but does not guarantee message order. A FIFO queue guarantees exactly-once processing and preserves the order of messages but has limited throughput compared to standard queues.

Quick Comparison

This table summarizes the main differences between AWS SQS Standard and FIFO queues.

Feature	Standard Queue	FIFO Queue
Message Ordering	Best-effort, no guaranteed order	Strict order preserved
Delivery	At-least-once (possible duplicates)	Exactly-once processing (deduplicated)
Throughput	Unlimited (scales horizontally)	Up to 300 messages/sec (can increase with batching)
Use Case	High throughput, flexible ordering	Critical order and no duplicates
Message Grouping	Not supported	Supports message groups for parallel processing
Cost	Lower cost per request	Slightly higher cost per request

Key Differences

Standard queues are designed for maximum throughput and scalability. They allow multiple copies of a message to be delivered, so your application must handle duplicates. Ordering of messages is not guaranteed, which means messages can arrive out of sequence.

FIFO queues guarantee that messages are processed exactly once and in the exact order they were sent. This is important for workflows where order matters, like financial transactions. FIFO queues use message groups to allow parallel processing while preserving order within each group.

Because FIFO queues enforce strict ordering and deduplication, they have lower throughput limits compared to standard queues. Standard queues can handle a very high volume of messages without ordering constraints.

Code Comparison

Here is how you create and send a message to a Standard queue using AWS SDK for Python (boto3):

python

import boto3

sqs = boto3.client('sqs')

# Create a standard queue
response = sqs.create_queue(QueueName='MyStandardQueue')
queue_url = response['QueueUrl']

# Send a message
sqs.send_message(QueueUrl=queue_url, MessageBody='Hello from Standard Queue')

Output

A message is sent to the standard queue without ordering guarantees.

FIFO Queue Equivalent

Here is how you create and send a message to a FIFO queue using AWS SDK for Python (boto3):

python

import boto3

sqs = boto3.client('sqs')

# Create a FIFO queue (name must end with .fifo)
response = sqs.create_queue(QueueName='MyFifoQueue.fifo', Attributes={'FifoQueue': 'true'})
queue_url = response['QueueUrl']

# Send a message with MessageGroupId
sqs.send_message(
    QueueUrl=queue_url,
    MessageBody='Hello from FIFO Queue',
    MessageGroupId='group1'
)

Output

A message is sent to the FIFO queue with guaranteed order and no duplicates.

When to Use Which

Choose a Standard queue when you need high throughput and can tolerate occasional duplicate messages or out-of-order delivery. This is ideal for tasks like background job processing where order is not critical.

Choose a FIFO queue when message order and exactly-once processing are essential, such as in financial systems, inventory management, or workflows that depend on strict sequencing.

Key Takeaways

Standard queues offer unlimited throughput but do not guarantee message order or uniqueness.

FIFO queues guarantee exactly-once delivery and preserve message order but have lower throughput limits.

Use standard queues for high-volume, flexible ordering scenarios.

Use FIFO queues when order and no duplicates are critical.

FIFO queues require a .fifo suffix in the queue name and use message groups for parallelism.