It might be that this behaviour happens especially because it is running on an embedded device. One of the things I will try to find out to make it easier to investigate this issue, is what size Nerves’ read/write partition has by default, and what happens if it were to get full.
How much is the overhead of CubDB’s internal tree structure?
I will try out if disabling the auto compaction helps, and I’ll build and share a minimal example that has the same behaviour as my real application (whose source I unfortunately cannot share).
In this case, I am saving a new value, which is an Elixir struct with about eight keys, containing some integers, strings and floats, under the key {:telegram "some_timestamp"} (where some_timestamp has the format "YYYYMMDDHHmmss").
Thank you very much for your responses 
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