Mendix 9.6 annoyingly slow

Dear Mendixers, does anyone of you have the same experience: I updated my Studio Pro to 9.6.0 (which really looks nice with the UI reworks) but its annoyingly slow: - on copying pages or flows - it feels laggy when modifying flows - switching between tabs is slow - closing tabs is slow - opening something from the App explorer is slow And MxAssist Bot is of course switched off and my dev machine is a quite beefy HP Zbook with I7, 32GB RAM and SSD.    I’m curious bout your answers!   Regards,  Franz
6 answers

Mendix 9.6.0 has significant performance issues with larger projects. As Juan mentioned I logged a support ticket with Mendix with a video and sample project on how to reproduce this. They sent it to their R&D teams for review but no feedback yet. However it’s unusable for me. It appears as if the error checking is interfering with the rest of the actions. And in our case error checking takes very long due to the size of the project. Most actions that occur during this error checking (that’s supposed to be in the background) freezes up the entire Studio Pro until the error checking completes. Even the error checking progress bar freezes up.


In 9.6.6 we, like Ivo, have significant performance issues in copying/pasting, opening and closing pages and flows, renaming stuff etc.. We came from 7.23.10 which work performant in everyway.

Things I've already done trying to improve things (no luck):

Set the error auto-check delay to 1000ms

Switched off Mendix Assist Logic Bot and Performance Bot

Also annoying is the bug in copy/pasting/delete in the properties pane. Come on guys, this is like several releases already?!

I'm running on a Dell XPS 11th gen i7-11800 with 32GB of RAM on a 1TB SSD so that shouldn't be a problem..


We just upgraded a big app from 7.23.19 to 9.6.6 but now also have this issue. In 7.23.19 it was working smoothly, but now it is really annoyingly slow… 25 % of my time I am waiting because of this slowness. Will also file a support ticket.


Please vote for my Idea to speed up Mendix Pro 9 👍



Hi all,

Could you please try it with 9.6.1 released today? We’ve identified an unfortunate issue in 9.6.0 that should be fixed in 9.6.1.

Sorry for inconvenience! :(


Hi Franz, thanks for your feedback and sorry to hear that you are experiencing performance issues. 

Regarding to your comment “MxAssist Bot is of course switched off”, our understanding is that the reported Studio Pro performance issues (including the ones in the past) are not primarily derived by MxAssist. 

Of course, MxAssist has impact on the performance, naturally. To minimize the performance impact, we’ve done several performance optimizations in 2021-Q2. Our testing shows that the performance optimizations have reduced server calls by 92% and User CPU usage by 35% on average. Please let us know if you experience negative performance impact by MxAssist.