SQS

SQS, or Amazon Simple Queue Service, is a fully managed message queuing service provided by Amazon Web Services. It enables decoupling and scaling of distributed applications by allowing components to communicate asynchronously through queues. SQS offers two queue types: Standard queues and FIFO (first-in-first-out) queues.

Standard queues provide high throughput, at-least-once delivery, and best-effort ordering. They are suitable for workloads where throughput matters more than strict ordering or perfect deduplication. FIFO queues guarantee exactly-once processing and preserve the order of messages within a queue, making them appropriate for tasks that depend on precise sequencing and deduplication.

Key features include messages up to 256 KB in size, configurable message retention from 1 minute to 14 days, and a visibility timeout that hides a received message from other consumers for a period while it is being processed. Long polling reduces empty responses, and dead-letter queues handle messages that fail processing repeatedly. SQS supports batch operations for sending and receiving multiple messages in a single call and optional server-side encryption via AWS KMS. Access is controlled with IAM policies; queues can be accessed from within Virtual Private Clouds using VPC endpoints for private connectivity. SQS integrates with other AWS services such as Lambda, SNS, and CloudWatch, enabling serverless event-driven architectures and monitoring.

Producers push messages to a queue; consumers poll, receive, process, and delete messages. If not deleted within the visibility timeout, messages reappear for others to process. SQS is designed to be highly available and scalable, with AWS handling maintenance and infrastructure.