- You can't keep building partitions forever
  - Space runs out for literal data, costs increase as data value decreases for old data
  - Memory runs out for indexes over partitions, e.g. in databuild itself
- We could introduce vacuuming?
- We could introduce partition want expiry callbacks?
- Jobs and job runs as partition edge transitions?
- Do we even want to delete partition entries? Can just wait till this is a problem.
- Partition want expiry events also enable non-event level reaction, e.g. vacuum for all events between time T1 and T2.
- RISK! If partition to partition data deps (via jobs that change, etc) are not canonical/stable:
  - We cannot assert the necessity of upstream partitions for anything longer than the initial job time to success (because it may have changed)
  - To make this valuable, we need to be able to assume that the reads/data deps from a singular parameterized job run are durable, because then we can propagate want times and have a durable "why does this partition need to exist"