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So let's discuss Amazon SQS long polling.

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So the idea is that when a consumer

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is requesting messages from a queue,

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it can wait for messages to arrive

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if there are none in the queue

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and this is called long polling.

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The reason you would do so is for twofolds.

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Number one, to decrease latency

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and number two, to reduce the number of API calls

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you are doing onto SQS.

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So let's see how this works.

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So we have SQS queue and it is empty.

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So our consumer is going to poll the queue

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and is going to poll it for up to 20 seconds.

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And the reason we do so is that

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if the queue is empty, we just wait.

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It's okay to just wait if the queue is empty

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so that when a message arises

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like it's just arriving in the message.

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If a consumer is still in the long poll

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then automatically that message will be sent

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to the consumer, which is with low latency

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and will automatically arrive as fast as possible.

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So this makes sense,

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long polling will decrease the number of API calls

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made to SQS while increasing the efficiency

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and decreasing the latency of your application.

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So you can configure it between one to 20 seconds

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with obviously the longer, the more preferable.

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And then you would obviously prefer, in my opinion,

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long polling to short polling.

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So make sure you configure it.

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And there are two ways to configure long polling.

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Either you configure it at the queue level

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such as any consumer doing a poll from the consumer

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will have long polling enabled

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or the consumer itself can choose to do long polling

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by specifying the wait timeout seconds.

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So anytime at the exam you see

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a way to optimize the number of API calls

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made to an SQS queue and decrease of latency,

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think about long polling.

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That's it for this lecture, I hope you liked it.

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And I will see you in the next lecture.