AWS API Gateway Throttling not working as expected

user_2444386 0
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I'm trying to enable API Gateway throttling, but it's not working as expected.

I set Default Method Throttling Rate to 1 request per second, and Burst to 1 request.

enter image description here

Then I created a loop in my code to make 10 simultaneous requests to my API endpoint.

for (let i=0; i<10; i++) {
    axios.get(url);
}

The expected result would be:

  • 1 successful request
  • 9 throttled requests (HTTP 429 error)

But the actual result was the opposite:

  • 9 successful requests
  • 1 throttled request (HTTP 429 error)

I repeated the process, but making 20 simultaneous request and the result was:

  • 16 successful requests
  • 4 throttled requests (HTTP 429 error)

On CloudWatch logs for this API method, I found different Log streams, each one with only few milliseconds difference.

enter image description here

If I set Rate to 0 requests per second and Burst to 0 request, the throttling works and ALL requests get throttlet. But when I set Rate and Bust to 1 it does not work as expected.

Why is that happening? I need to limit my API to only 1 request per second.

aws-api-gateway aws-lambda amazon-web-services throttling
2 Answers

It seems AWS API Gateway throttling is not very precise for small values of rate/burst.

I imagine that there are multiple "instances" of the API Gateway running, and the values of rate and burst are "eventually consistent".

However I did not find any documentation about that.

When I made an initial request and wait 500 milliseconds before making other 99 requests, the results were "less imprecise".

Example:

axios.get(url);
setTimeout(function(){
    console.log("After 500 ms");
    for (let i=0; i<99; i++) {
        axios.get(url);
    }
}, 500);

Results:

  • Once I got 1 success and 99 throttles.
  • Other time I got 12 success and 88 throttles.
  • Other time I got 33 success and 67 throttles.

However, it's difficult to have consistent results.

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