Handling Order of Firestore Events for Synchronization with Typesense.

.database.ref(`tasks/{itemId}`)
.onWrite(async (change, context) => {
  /**
   * We use a Firestore transaction to create a "lock" at a DB location
   * for a given `itemId`
   */
    const { timestamp, eventId } = context;
    const { itemId } = context.params;
    const timestampRef = firestore
      .collection(`typesenseLocks_tasks`)
      .doc(itemId);
    await admin.firestore().runTransaction(async transaction => {
      const dataChangedTimestamp = new Date(timestamp).getTime();
      const lastUpdatedTimestampDoc = await transaction.get(timestampRef);
      const lastUpdatedData = lastUpdatedTimestampDoc.data();

      /**
       * If this is the first time this document was changed (no previous locks),
       * or the last-stored lock timestamp is older than the current event's timestamp,
       * prepare a payload and send to Typesense.
       */
      if (
        (!lastUpdatedData?.timestamp ||
          dataChangedTimestamp > lastUpdatedData.timestamp) &&
        lastUpdatedData?.eventId !== eventId
      ) {
        // Send to Typesense
        await updateTypesense(change, indexer, itemId);

        // Finalize Transaction
        transaction.set(timestampRef, {
          timestamp: dataChangedTimestamp,
          eventId
        });
      } else {
        /**
         * Do nothing, current event is older than last-indexed event already recorded, can be safely discarded
         */
      }
    });

  for (let i = 0; i < 300; i++) {
    promises.push(ref.child("tasksOpen").child(taskId).child("name").set(`A ${i}`));
    console.log("Set name to", i);
  }

  await Promise.all(promises);