Rare crash during DDC fill: FMemoryDerivedDataBackend MaxCacheSize assertion

Hello,

We’re trying to generate a DDC Pak using the following command to speed up loading on slower machines:

UE4Editor-Cmd.exe <Project> -run=DerivedDataCache -fill -DDC=CreateInstalledProjectPak -TargetPlatform=Windows

In extremely rare cases, the process fails with this assertion:

Assertion failed: SerializationSpecificDataSize + DataSize <= MaxCacheSize || MaxCacheSize <= 0

The crash occurs in FMemoryDerivedDataBackend::SaveCache() and seems to happen unpredictably — most of the time the DDC generation succeeds without issue. However, under certain conditions, it hits the MaxCacheSize limit.We’re considering either disabling the in-memory cache entirely or increasing the MaxCacheSize.

Is increasing MaxCacheSize a valid and stable long-term solution? Could it cause issues for users with low-end setups (limited RAM/CPU) when launching the editor or project?

Is it necessary to delete the previous cache if the project has been changed?

Engine/DerivedDataCache/

Project/Saved/DerivedDataCache/

[Image Removed]

P.S. Unfortunately, I’ve lost all crash report files. If it happens again, I’ll attach them if needed.

Hey, sorry for the delay. We deprecated the boot cache in UE 5.0. Its original purpose, 11 years ago, was to mitigate the seek time overhead on hard disks. With solid state drives being the norm for years now, the benefits of a “boot cache” are outweighed by issues like the one you are reporting. I recommend removing the boot cache from all of the DDC graphs in BaseEngine.ini and/or DefaultEngine.ini.