parallel.js

export const saveBooks = async (books) => {
  const chunks = chunk(chunk(books, 100), 10)

  const results = []

  for (const chunkOfChunks of chunks) {
    const chunkResults = await Promise.all(chunkOfChunks.map(saveBooksChunk))

    results.push(...chunkResults)
  }

  return results
}