Email alerts hitting Resend rate limit (2 req/s)

[louis030195]

Problem

Email alerts are failing due to Resend API rate limiting:

2025-12-01 23:31:24.612 [info] Sending email with from: "alerts@alerts.mediar.ai"
2025-12-01 23:31:24.678 [error] Resend error: {
  statusCode: 429,
  name: 'rate_limit_exceeded',
  message: 'Too many requests. You can only make 2 requests per second. See rate limit response headers for more information. Or contact support to increase rate limit.'
}

Root Cause

Resend free/starter tier limits to 2 requests per second. When multiple workflow executions fail simultaneously (e.g., batch runs), we exceed this limit.

Potential Solutions

1. Queue emails with rate limiting - Implement a simple queue that throttles to 1-2 emails/second
2. Batch/aggregate alerts - Combine multiple failures into a single email (e.g., "3 workflows failed in the last minute")
3. Upgrade Resend plan - Higher tiers have increased rate limits
4. Add retry with exponential backoff - Retry failed emails after delay

Impact

Alert emails may be lost when multiple executions fail at the same time, reducing visibility into workflow failures.