Amazon SNS and Amazon SQS both offer Standard and FIFO variants of topics and queues respectively which helps you build better micro-service focused, de-coupled applications. Some of the basic understanding of SNS and SQS with the technology and concepts behind is explained in - {%post aws-builders/getting-started-with-sns-and-sqs-3m4i %} The previous blog post explains about when and how to choose SNS or SQS for your application need. {%post aws-builders/when-to-sns-or-sqs-2aji %} And this blog post, will give you a better understanding of Standard and FIFO variants of topics and queues.
What is Standard topic/queue?
Standard topics/queues are used often when the system can handle messages which can arrive more than once and without a proper order.
What is FIFO topic/queue?
FIFO topics/queues follows the concept of First-in,First-out which guarantees the order of messages is very necessary. This strictly maintains the order of the message and also doesn't deliver the same message multiple times.
Standard v/s FIFO : SNS
Amazon SNS offers topics of two variants - Standard topics and FIFO topics.
| Feature | Standard topics | FIFO topics |
| Throughput | Nearly unlimited no. of messages per second. | 300 messages per second or 10 MB per second (whichever is first). |
| Message order | Order of messages will not be same as published order. | Order is maintained by following first-in-first-out (FIFO). |
| Message delivery | At-least once, can duplicate again. | Only once. |
| Subscription types | Amazon SQS, Amazon Kinesis Data Firehose, AWS Lambda Fns, HTTPS, SMS, Email, mobile push. | Only SQS FIFO queues. |
| Limits | 100,000 standard topics with 12.5M subscriptions per topic per account. | 1,000 FIFO topics with 100 subscriptions per topic per account. |
| Encryption (via AWS KMS) | Both at rest and in transit. | Both at rest and in transit. |
| Pricing (more info in SNS pricing) | First 1M requests free, $0.5 per 1M requests. | Publish and publish batch API requests are $0.30 per 1M and $0.017 per GB of payload data and subscription messages are $0.01 per 1M and $0.001 per GB of payload data. |
| Use-case | Whenever there is multi-subscriber scenario, Whenever the application can handle duplicate and unordered messages. | Whenever the need for ordering is a must. |
Standard v/s FIFO : SQS
Amazon SQS offers queues of two variants - Standard queues and FIFO queues.
| Feature | Standard queues | FIFO queues |
| Throughput | Nearly unlimited number of transactions per second per API action | 300 message per second with a batch of 10 messages per operation. |
| Message order | Occasionally order of messages will not be same. | Order is maintained by following first-in-first-out (FIFO). |
| Message delivery | At-least once but can get a copy of the same message | Only once. |
| Message persistence | Max upto 14 days. | Max upto 14 days. |
| Encryption (via AWS KMS) | Both at rest and in transit. | Both at rest and in transit. |
| Resolvers / Triggers | Lambda Fns and SNS topics. | Lambda Fns and SNS topics. |
| Pricing (more info in SNS pricing) | First 1M requests free, $0.4 for 1M-100B requests, $0.24 for over 200B requests. | First 1M requests free, $0.5 for 1M-100B requests, $0.35 for over 200B requests. |
| Use-case | Whenever the application can handle unordered and multiple delivery of messages such as decoupling transaction ordering process, batch processes. | Whenever the message have to be ordered such as image/video decoding/encoding, using as subscriber to a FIFO topic. |
Conclusion
Whenever choosing SNS or SQS choosing between Standard variant and FIFO variant is also necessary as the features of message ordering, exactly once delivery would help building efficient systems.
