SQS Lambda Trigger polling rate

Question

I'm trying to understand how SQS Lambda Triggers works when polling for messages from the Queue.

Criteria

I'm trying to make sure that not more than 3 messages are processed within a period of 1 second.

Idea

My idea is to set the trigger BatchSize to 3 and setting the ReceiveMessageWaitTimeSeconds of the queue to 1 second. Am I thinking about this correctly?

Edit:

I did some digging and looks like I can set a concurrency limit on my Lambda. If I set my Lambda concurrency limit to one that ensures only one batch of message gets processed at a time. If my lambda runs for a second, then the next batch of messages gets processed at least a second later. The gotcha here is long-polling auto scales the number of asychronous polling on the queue based on message volume. This means, the lambdas can potentailly throttle when a large number of messages comes in. When the lambdas throttle, the message goes back to the queue until it eventually goes into the DLQ.

user_7661119 · Answer

ReceiveMessageWaitTimeSeconds is used for long polling. It is the length of time, in seconds, for which a ReceiveMessage action waits for messages to arrive (docs). Long polling does not mean that your client will wait for the full length of the time set. If you have it set to one second, but in the queue we already have enough messages, your client will consume them instantaneously and will try to consume again as soon as processing is completed.

If you want to consume certain number of messages at certain rate, you have do this on your application (for example consumes messages on a scheduled basis). SQS by itself does not provide any kind of rate limiting similar to what you would want to accomplish.

SQS Lambda Trigger polling rate

1 Answers