Amazon’s Simple Queue Service (SQS) recently gained FIFO (first-in, first-out) queues, which are designed to « guarantee that messages are processed exactly once, in the order that they are sent, and without duplicates ». AWS rolled out this new queue type in the US East (Ohio) and US West (Oregon) regions and « plans to make it available in many others in early 2017 ».
Amazon SQS is described as a « fast, reliable, scalable, fully managed message queuing service [designed to] decouple the components of a cloud application [and] transmit any volume of data, without losing messages or requiring other services to be always available ».
Accordingly, a notable characteristic of the service has been the de facto absence of scaling limits for the now called ‘standard’ queues, insofar users can create an unlimited number of queues, and each queue provides « nearly unlimited throughput » by default. However, this effortless scaling mode requires a message processing architecture that can only guarantee best-effort ordering and at-least-once delivery.
These standard SQS queues are now complemented by a new FIFO queue type, which trades unlimited scaling for stronger message ordering and processing guarantees, based on AWS’ observation that « customers have told us that FIFO applications are generally lower-throughput – 10 messages per second or lower »:
The underlying architectural tradeoffs and resulting constraints are described in more detail in a technical blog post on how the Amazon SQS FIFO API works.
