this was the impl

Do($ => {
  const items = $(importPickItems(req.items))
  $(
    items.batchNPar(
      10,
      Ship.validateItem,
      items =>
        PickItems$.update(PickListRepository.logIf(items => ClientEvents.of.PickItemsUpdated({ items })))
          .runTerm(items)
          .flatMap(([items, events]) => PickListRepository.save(items, events))
    )
      .withValidationCache
  )
})

/**
 * @tsplus pipeable Collection batchNPar
 * @tsplus static Collection.Aspects batchNPar
 */
export function batchNPar<R, E, A, R2, E2, A2, T>(
  n: number,
  forEachItem: (i: T) => Effect<R, E, A>,
  forEachBatch: (a: Chunk<A>) => Effect<R2, E2, A2>
) {
  return (items: Iterable<T>) =>
    items.chunk(n)
      .forEachEffectPar(_ => _.forEachPar(forEachItem).flatMap(forEachBatch))
}