The requested URL returned error: 429 Too Many Requests

Question

I am reaching out on behalf of the Greek National Federation of Blind people. Our website is [www.eoty.gr] . It is a WordPress website that gets daily updated with 15 new blog posts. Some of our users are not familiar with the screen reader, so we have created a landline service through which they can listen to our website’s content.

Tht landline service uses WordPress RSS feed API combined with Microsoft Azure’s Text to Speech service.  So, the user dials a landline number and listens to the article’s titles. Then they choose which article they want to listen to. During the last few weeks/ or months we are facing several problems. The titles are not being produced anymore. We are receiving the following error response from Microsoft Azure:  The requested URL returned error: 429 Too Many Requests We understand that recently you made changes to your free plan. You used to offer  5 million characters for free per month and you dropped it to 500.000.  So we expected that each month ( when they TTS Service refreshes ) , our Voice Service would work for several days until that limit was reached and then it would stop working until it was time to refresh the service. However we notice that the voice service works for few days, then stops working, then after few days it works properly again. We are confused by this irregularity. Can you please let us know why we are receiving this message 429 error and why the service works sporadically?

Answer 1

Hi EOTY

The 429 "Too Many Requests" error you're encountering from Microsoft Azure's Text to Speech (TTS) service is due to exceeding the request rate or character quota limits of your subscription. Microsoft recently reduced the free tier from 5 million to 500,000 characters per month, which means your service may hit the limit quickly if you're generating audio for multiple blog posts daily.

The sporadic behavior—where the service works for a few days, then stops, and later resumes—is likely caused by Azure's internal throttling mechanisms, which temporarily block requests when usage spikes or concurrency limits are exceeded. This throttling can occur even if the monthly quota hasn't been fully consumed. To resolve this,

1. Need to Check Request Frequency: Analyze the frequency of requests being made to the Text to Speech service. Ensure that the requests are within the allowed limits
2. Optimize Request Handling: Implement backoff retry mechanisms to control the rate of requests sent to the Text to Speech service. Consider implementing delays between requests to stay within the limits.
3. Monitor Usage: You can enable diagnostics setting on your speech resource and regularly monitor the usage of the Text to Speech service to understand the pattern of requests and identify any spikes that may lead to the "429 Too Many Requests" error.
4. Review Free Plan Limit and upgrade quota is being fully used: Since there was a change in the free plan from 5 million characters to 50000 characters per month, ensure that the service usage aligns with the new limit. Feel free to upgrade to use higher tier.

For troubleshooting we need to monitor the request patterns and frequency to identify any spikes and check the logs or analytics of the Text to Speech service to understand the request volume and also Review the implementation of the landline service to ensure requests are optimized.

Resources:

• Monitor Speech Service
• Azure Monitor Documentation
• Speech Service Quotas and Limits

Hope it helps!

Thanks

Answer 2

Hi.

Here is the quota limit for F0 tier:

Apart from the overall quota limit, there are also rate limits for F0. Make sure that you don't go over these limits.

Another reason for getting 429 error is that the TTS service is currently scaling out as there are more requests, and you might need to wait for a while until the scale is complete.

If you know you may be using the service over the F0 limit, S0 tier is recommended, as you can apply for a quota increase if you are going beyond 200 TPS.