Customers building event-driven applications on AWS rely on Amazon Simple Queue Service (Amazon SQS) and AWS Lambda event source mappings (ESMs) to process millions of events every day. The fully managed polling infrastructure of ESMs eliminates the need to write and maintain custom code. You can focus on business logic while Lambda handles scaling, batching, and error handling automatically. As workloads grow, many customers need to meet demanding requirements for low-latency message processing, high-concurrency execution, and high-throughput event processing.
Use cases such as real-time payment processing, fraud detection, IoT telemetry pipelines, and flash-sale order fulfillment require the ESM to scale rapidly and sustain peak performance without queue backlog. To address these needs, AWS launched provisioned mode for SQS event source mappings. Provisioned mode gives you direct control over the number of event pollers assigned to your ESM for predictable and rapid scaling. With Provisioned mode, you can configure event pollers up to 10,000, supporting concurrency of up to 100,000 concurrent Lambda executions and throughput of 10 GB/s.
You can process up to a million events per second. Provisioned mode is also available for Apache Kafka event source mappings including Amazon Managed Streaming for Apache Kafka (Amazon MSK) and self-managed Kafka. When you configure an SQS queue as an event source for a Lambda function, Lambda automatically creates an ESM resource. The ESM manages a fleet of internal event pollers that continuously poll the SQS queue, retrieve messages, and invoke your Lambda function with batches of events.
In default ESM mode, Lambda automatically manages the number of event pollers based on queue depth and processing throughput. The system starts with five pollers and scales up as the queue backlog builds, supporting up to 1,250 concurrent invocations. This automatic scaling works well for the majority of event processing workloads. However, the scale-up rate in default mode (approximately 300 additional concurrent executions per minute) can leave latency-sensitive workloads with growing queue backlogs during sudden traffic spikes.