I'm trying to understand how rate limiting works for REST API calls. I was informed that it's based on the number of concurrent requests, which I can live with, but I can't figure out what the permitted number of parallel requests is. I've setup a simple test to make 16 parallel requests using the following shell script:

for ((request=1;request<=4;request++))
    for ((x=1;x<=4;x++))
  curl --header "Content-Type: application/json" \
  --header "Authorization: Bearer 7gPInMQYW5rxE2G2F4sZXXXX" \
  --request POST \
  --data '{"email": "eliot@eliot.com.au", "validators": [ "SyntaxValidator", "MXValidator", "ListDetectiveValidator" ] }' \
  https://www.exacttargetapis.com/address/v1/validateEmail &

This returns a successful response for approx 80% of the requests, but returns the following response with a 500 HTTP status code for others:

   "message":"Internal Server Error",

I have also tried using Tenant Specific Endpoints and OAuth2, but I get the same result.

I would assume if this is a rate limiting reason, then it would respond with a documented rate limiting response and 429 HTTP status code.

If I replay the same failed request, then it works 99% of the time, second time around.

I've tried different REST API routes and this issue appears consistently across all of them (so it's not specific to an API method).

Obviously, I can make consecutive requests instead of concurrent, but this is very inefficient.

How do others approach concurrent REST API requests for Marketing Cloud?

  • 2
    There is currently an issue on this route where sometimes you receive a 500 error, the 500 error is not caused by a rate limit
    – EazyE
    Apr 23 '19 at 16:46
  • Hello @EazyE, thanks for confirming that this is an issue an is not expected behavior. I only tested two routes; validateEmail and /guide/v1/emails (used to return interpreted email content). I've built a solution that uses the latter method and I'm keen to see this fixed too. Apr 23 '19 at 20:29
  • Have you seen these 500 errors no longer occur on the validate route?
    – EazyE
    Apr 24 '19 at 20:49
  • Hello @EazyE, thanks I can confirm that there are no longer 500 errors on the Validate route. Can we expect to see a fix for the Emails route too? Apr 28 '19 at 10:28

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