A technique I've used before is to treat Elasticsearch as rebuildable at any time, consider this approach:
A cron runs every 5 minutes that looks at your database for any objects you're indexing where last_modified_at timestamp > last_indexing_started_timestamp.
Index the objects into Elasticsearch, then update the last_indexing_started_timestamp value to be when you started the original sync process, so we catch any modified objects between the start/end of the update run, next run.
Then if Elasticsearch needs rebuilding you can just clear out the last indexing timestamp and resync from the start of time, and its self-recovering / won't get out of sync.
A cron runs every 5 minutes that looks at your database for any objects you're indexing where last_modified_at timestamp > last_indexing_started_timestamp.
Index the objects into Elasticsearch, then update the last_indexing_started_timestamp value to be when you started the original sync process, so we catch any modified objects between the start/end of the update run, next run.
Then if Elasticsearch needs rebuilding you can just clear out the last indexing timestamp and resync from the start of time, and its self-recovering / won't get out of sync.