TL;DR
Make items held by the inserter not spoil for max-efficient, lock-free factory.What?
Items held by the inserters doesn't spoil.Why?
Consider this case:1. Inserter picks up item that is about to spoil.
2. While the inserter arm is mid-air, the item spoils.
3. The target machine doesn't accept spoilage, so the inserter is stuck at this state and so does the target machine.
When feeding biter spawner, it is more efficient to use most spoiled item first because the nutrient value doesn't get affected by the freshness of the bioflux.
However, after configuring the inserters to pick up most spoiled item first, I noticed some biter spawner starvation due to the inserter trying to insert spoilage to spawner.
After setting the priority to fresh one I never experienced the issue, but I hope there's a way to maximize bioflux efficiency while not worrying about inserter locking.
Note: After writing this, I found the lua api flag enter_drop_mode_if_held_stack_spoiled(https://lua-api.factorio.com/latest/pro ... ck_spoiled), probably suggesting this is an expected behavior. Please disregard this suggestion if setting the priority to fresh one is the intended solution.