1. Validation Errors: Your event data might not be properly formatted or might contain invalid values.
When events fail validation, Mixpanel returns a 400 status code with details about the failed records. For example:
{
"code": 400,
"error": "some data points in the request failed validation",
"failed_records": [
{
"index": 0,
"$insert_id": "8a66058c-a56d-4ef6-8123-28b7c9f7e82f",
"field": "properties.time",
"message": "properties.time' is invalid: must be specified as seconds since epoch"
}
],
"num_records_imported": 23,
"status": "Bad Request"
}
Check your event properties, especially timestamp formats and ensure all strings are valid UTF-8 Import Events Validation.
2. Rate Limiting: You might be hitting Mixpanel's rate limits.
Mixpanel enforces a rate limit of 2GB of uncompressed JSON/minute or ~30k events per second. If you exceed this limit, you'll receive a 429 response code Rate Limits.
3. Authentication Issues: Ensure you're using the correct project token or authentication credentials.
For server-side implementations, consider using the /import endpoint instead of /track as it's more suitable for server-side integrations Track Events.
4. Event Size Limits: Each event has size constraints:
- Must be smaller than 1MB of uncompressed JSON
- Must have fewer than 255 properties
- Nested objects must have fewer than 255 keys with max nesting depth of 3
- Arrays must have fewer than 255 elements
