curl --request POST \
  --url https://your-instance.example.com/api/filters.backfillStart \
  --header 'Content-Type: application/json' \
  --data '
{
  "workspace_id": "<string>",
  "lookback_days": 183,
  "chunk_size_days": 15.5,
  "batch_size": 25050
}
'

{
  "task_id": "550e8400-e29b-41d4-a716-446655440000"
}