Have flags/options in Subject Request API (SR API) to not receive the entire batch of opted-out records.
For example,
1) subset=mine. Only send ID's in my DL or API subset.
2) release=x. Only send ID's opted out since that release date. release=17 would return opt-outs submitted since launch date of release 17.
3) use a date range. This way a customer can parse daily, weekly or whatever cadence fits their use case.