ZenServer is slow to initialize when launching multiple editor processes

In [Content removed] I reported issues with ZenServer when running multiple editor processes in 5.4. We’ve since upgraded to 5.5, and it has generally been a big improvement over 5.4 in this regard, but recently we’ve started seeing the following when running our suite of 7 editor processes on CI agents:

[2025.05.22-03.33.05:399][ 0]LogZenServiceInstance: Found Zen config default=C:/Users/omega_automation/AppData/Local/UnrealEngine/Common/Zen/Data [2025.05.22-03.33.05:399][ 0]LogZenServiceInstance: InTree version at 'C:/BuildAgent/work/454e66fa4e22255b/Engine/Binaries/Win64/zenserver.exe' is '5.5.7-202409112143-windows-x64-release-f523a01' [2025.05.22-03.33.05:406][ 0]LogZenServiceInstance: Installed version at 'C:/Users/omega_automation/AppData/Local/UnrealEngine/Common/Zen/Install/zenserver.exe' is '5.5.7-202409112143-windows-x64-release-f523a01' [2025.05.22-03.33.10:407][ 0]LogZenServiceInstance: Warning: Local ZenServer AutoLaunch initialization timed out waiting for other process to complete startup/recovery [2025.05.22-03.33.10:407][ 0]LogZenServiceInstance: Awaiting ZenServer readiness [2025.05.22-03.33.10:908][ 0]LogZenServiceInstance: Found existing instance running on port 8558 matching our settings, no actions needed [2025.05.22-03.33.10:909][ 0]LogZenServiceInstance: Display: Unreal Zen Storage Server HTTP service at [::1]:8558 status: OK!. [2025.05.22-03.33.10:909][ 0]LogZenServiceInstance: Local ZenServer AutoLaunch initialization completed in 5.511 secondsWe’re already supplying `-Multiprocess` and `-MultiprocessID` arguments to these processes to deal with some other issues relating to running multiple editor processes at once.

Could the fact that we’ve only started hitting this some time after upgrading to 5.5 be due to the fact that the Zen data directory has grown in size over time? Is there some non-constant time process on startup like verifying the contents of the cache?

Is there anything we can do that would allow us to get this working quicker and avoid seeing this warning, please? Could some work please be done to speed up ZenServer initialization in future engine versions?

Steps to Reproduce

Zen startup time is affected by the amount of content in it’s data directory - it needs to read the state and index all know data, this involves reading multiple index files with optional log files.

It is usually fairly quick but if the data directory contains a lot of data it will take time.

Have a look at the zenserver log files to get an indication of how long it takes for zenserver to start.