Hello,
We had some concern also once about MGM memory. Abnormal memory usage of the MGM (QDB namespace)
The conclusion for us was that someone launched the eos find command on the whole instance’s namespace, and the process went on forever, filling some buffer until the whole search was finished, then memory was freed. But this was not a but step like yours, more sustained increase during many days, just before a sudden free.
In addition, we were using values bigger than the default for the eos ns cache because we had available memory, and this was threatening memory outage. But this seems to be not useful (no performance gain, and bigger memory usage), so better keep the default values.
In general, we still observe that even after the cache maximum is reached, the MGM (v4.5.15) memory usage steadily, but slowly, always increases (~+50GB in 3 months)