Digital Messaging API 429 errors under concurrent load in US1

General Discussion
1

Context:
We are currently validating the capacity of the Digital Messaging channel in the US1 environment. The goal is to determine the maximum throughput for incoming chat sessions before the system starts rejecting connections. We are using JMeter 5.6 to simulate a burst of concurrent users initiating chats via the /api/v2/conversations endpoint. The test plan creates 100 concurrent threads, each sending a POST request to start a new chat session with a specific routing configuration. We are using the standard OAuth2 client credentials flow for authentication, ensuring tokens are refreshed before expiration. The Architect flow is a simple direct route to an agent group with no complex logic or external integrations.

Question:
Need some help troubleshooting why we are seeing HTTP 429 Too Many Requests errors after only 15 concurrent sessions are established. The error response body indicates that the rate limit has been exceeded for the application. However, the documentation suggests that the rate limit should be higher for conversation creation. We have verified that the requests are being sent at a rate of one per second per thread, which seems well within reasonable limits. The 429 errors occur consistently when the number of active conversations exceeds 15, regardless of whether the agents are available or not. We are not seeing any 500 Internal Server Errors, which suggests the backend services are healthy, but the gateway is throttling the requests. Is there a specific configuration in the Architect or the Application settings that limits the number of concurrent chat initiations? We have checked the application’s rate limit settings, but they appear to be set to the default values. Any insights into how to increase this limit or how to structure the test to avoid hitting this threshold prematurely would be appreciated. We want to ensure that our system can handle peak load without dropping customer chats.

2

The best way to fix this is to implement exponential backoff in your JMeter script. Genesys Cloud enforces strict rate limits on the conversations endpoint to protect the platform.

You need to catch the 429 response and wait before retrying. This mimics real-world agent behavior and prevents the API from throttling your test load.

3

This is a classic case of hitting the API gateway’s burst limit rather than the sustained throughput ceiling. The 429 response indicates the rate limiter is active, so adjusting the concurrency settings in your JMeter thread group is the primary fix.

4

the backoff idea is good but in java sdk we usually check the Retry-After header directly. just waiting a fixed time might still fail if the server is busy.

here is a quick snippet using the rest client. it parses the header and sleeps for that exact amount.

Response response = client.execute(request);
if (response.getStatus() == 429) {
 String retryAfter = response.getHeader("Retry-After");
 if (retryAfter != null) {
 try {
 Thread.sleep(Long.parseLong(retryAfter) * 1000);
 } ch (NumberFormatException e) {
 // fallback to 1s if header is weird
 Thread.sleep(1000); 
 }
 }
}

also make sure you are using the correct region endpoint. us1 has different limits than eu1 sometimes. if you hit the limit too hard the edge might block the ip temporarily. better to ramp up slowly in jmeter instead of 100 threads at once.

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5

rate limiting is the main issue here. if you’re hitting 429s, the platform is protecting itself.

for jmeter tests, don’t just add a random wait. check the Retry-After header in the response. it tells you exactly how long to pause.

in jmeter, you can use a JSR223 PostProcessor (Groovy) to grab that value and apply a SampleTimeout or a simple sleep().

def retryAfter = prev.getResponseHeader("Retry-After")
if (retryAfter != null) {
 long waitTime = Long.parseLong(retryAfter) * 1000 // convert seconds to ms
 SampleResult.setResponseMessage("Rate limited. Waiting ${waitTime}ms")
 Thread.sleep(waitTime)
}

this stops the test from failing immediately. it mimics a real user who just waits a bit if the chat is busy.

also, 100 concurrent threads is a lot for a single test. try lowering it to 20 or 30 first. see if the 429s disappear. if they do, the issue is just the burst size.

1 Like