Scaling and concurrency in Lambda - AWS Lambda

Scaling and concurrency in Lambda

Lambda is engineered to provide managed scaling in a way that does not rely upon threading or any custom engineering in your code. As traffic increases, Lambda increases the number of concurrent executions of your functions.

When a function is first invoked, the Lambda service creates an instance of the function and runs the handler method to process the event. After completion, the function remains available for a period of time to process subsequent events. If other events arrive while the function is busy, Lambda creates more instances of the function to handle these requests concurrently.

For an initial burst of traffic, your cumulative concurrency in a Region can reach between 500 and 3000 per minute, depending upon the Region. After this initial burst, functions can scale by an additional 500 instances per minute. If requests arrive faster than a function can scale, or if a function reaches maximum capacity, additional requests will fail with a throttling error (status code 429).

All AWS accounts start with a default concurrent limit of 1000 per Region. This is a soft limit that you can increase by submitting a request in the AWS Support Center.