Resolving the "Rate Exceeded" Error During SSO Login with Amazon Cognito

Problem

Users attempting to log in via Single Sign-On (SSO) with Amazon Cognito may encounter a "Rate Exceeded" error message, accompanied by an HTTP 429 status code. This indicates that the number of authentication requests has surpassed the allowed rate limit.

Root Cause

Amazon Cognito enforces rate limits on API operations to ensure fair usage and maintain service stability. When the number of requests exceeds the defined thresholds, the service returns a 429 status code to signal that the client should slow down. These limits are categorized by operation type and region.

Solution

To mitigate and resolve the "Rate Exceeded" error:

1. Implement Exponential Backoff: Introduce a delay between retry attempts. Start with a small delay and progressively increase it after each subsequent failure. This approach helps in reducing the load on the server and increases the chances of a successful request.
2. Monitor API Usage: Regularly check your application's API request metrics to identify patterns and potential spikes in usage. This can help in proactively managing request rates.
3. Request Rate Limit Increases: If your application consistently requires higher request rates, consider requesting a rate limit increase from AWS Support. Note that increases are granted on a per-region basis.
4. Optimize Authentication Flows: Review and optimize your authentication processes to minimize unnecessary API calls. For instance, avoid redundant login attempts and ensure that tokens are reused appropriately.

Additional Resources

• Amazon Cognito Quotas Documentation
• Managing API Request Rate Quotas