Pulseri Requests to the API are now capped at 256 KB. Traits, event properties, survey answers and webhook payloads accept up to 100 keys per object, key names up to 255 characters, and nesting up to three levels deep. A request over a limit is refused with a clear error and nothing is stored. Data you already have is unaffected and stays readable.
Event tracking also checks your people allowance before it stores anything, so a visitor over the limit leaves no data behind.
See the REST API guide.