Persistent storage
Files that outlive the machine that made them.
A sandbox filesystem is gone when the session ends. That is correct for scratch space and wrong for anything a later run needs.
Across runs of a task
Files written to the task's storage area survive the session. A nightly job can leave state for tomorrow's run without you running a database for it.
Or suspend instead
When the gap is short and the state is large, suspending keeps the whole filesystem intact and stops paying for the machine. Terminating and re-fetching costs time; suspending costs storage. Which is cheaper depends on the size and the gap.
Results you actually care about should leave the
sandbox — written to your own store, or read out by the caller. Storage
that opsen manages is a convenience, not a system of record.