Mixpanel does not have any rate limit on the amount of events or people updates you send our way. Queries made from reports hosted on mixpanel.com are not limited (with the exception of our newly released JQL product, whereby there is a 5 GB max of data that can be processed in a single query, and a 2 GB max for data output in the table below);
However for the formatted and raw API endpoints, the rate-limit rules per project are as follows:
Formatted API Rate Limit: 60 requests per rolling 60 seconds for up to 5 concurrent connections
Raw Export API Rate Limit: 1 request connection at any given time
If you exceed the rate-limit, a 502 error can be thrown, and the export request can be denied. As of now, we don't really make exceptions on this, as allowing more connections/queries can adversely affect our ability to scale and support all of our users.
If you do run into any rate-limiting issues, you will want to configure your set-up on your end so that once you've queried for data within a given time-range, you will not need to query for any overlapping data again. This will minimize the likelihood of you running into our API limits.