EventBus is capable of sending events in batches. Currently there's no limit in the size of an outgoing batch, which could be problematic, for example if a MassMessage job with a large message is submitted to a large number of users, the overall EventBus extension -> eventgate request size could exceed the limits set up in eventgate (or exceed any common sense size of a POST body).
We need to introduce a config variable with the max size of a batch (probably in bytes, not messages) and attempt to chop up large batches into smaller ones. Ideally the configuration value should be synchronized with eventgate settings.