medium_mongodb_performance_parallel_fetching

parallel.ts

async function getQuotesForPeriod(
  assetIdentifier: string,
  from: Date,
  to: Date
): Promise<Quote[]> {
  const quotesCollection = await getQuotesCollection();

  /**
   * When fetching multiple years of data, queries are fast, but retrieval not so much.
   * To improve query performance, we split the interval into a few chunks and query/fetch the data in parallel,
   * improving read throughput.
   */

  const intervals = chunkInterval(from, to).reverse(); // descending

  const all = await Promise.all(
    intervals.map(async (interval) => {
      return quotesCollection
        .find(
          {
            isin: assetIdentifier,
            date: { $gte: interval.start!, $lte: interval.end! },
          },
         
        )
        .sort({ date: -1 })
        .toArray()
    })
  );

  return all.