The performance issues aren't with the measurement requests but with reporting.
When I eval'd it for my book last fall there were big delays in reporting waiting for segments and then also issues with custom reports. I think they have changed the default behavior to get around some of the former, but with MySQL it's always going to be tough for larger queries.
(if there's any performance issue on the measurement side it has more to do with the JavaScript payload because they include a lot in their standard JS bundle).
For self-hosted, if you are doing into the tens of thousands of pageviews per day you may want to turn off real-time and switch to auto-archiving which pregens reports. That level of traffic depends a lot though on the report period you are running against and how big you've provisioned your MySQL server. YMMV and I haven't benchmarked at multiple traffic levels.
When I eval'd it for my book last fall there were big delays in reporting waiting for segments and then also issues with custom reports. I think they have changed the default behavior to get around some of the former, but with MySQL it's always going to be tough for larger queries.
(if there's any performance issue on the measurement side it has more to do with the JavaScript payload because they include a lot in their standard JS bundle).