It groups max 50 requests into one bulk requests and issues multiple requests if needed.
Assuming a request line has about 500 bytes, we are looking at around max 25KB... 25KB for a POST requests really shouldn't be any huge. Even 100K or 1MB shouldn't be any problem in theory. PHP default is 8MB.
We could also make things more complicated and limit by number of characters but hoping it is not needed.