const joinEvent = async (user, payload) => {
  const { userId } = user;
  const { eventId, slotId, data } = payload;

  const session = await mongoose.startSession();
  session.startTransaction();

  validateFields(payload, ["eventId", "price", "data"]);

  const [event, slot] = await Promise.all([
    Event.findById(eventId),
    EventSlot.findById(slotId),
  ]);

  if (!event || !slot)
    throw new ApiError(
      status.NOT_FOUND,
      `${event ? "Slot" : "Event"} not found`
    );

  if (event.status !== ENUM_EVENT_STATUS.OPEN)
    throw new ApiError(
      status.BAD_REQUEST,
      `Event is no longer open (status: ${event.status}).`
    );

  // check seat availability
  const totalPeople = slot.currentPeople + 1;
  if (totalPeople > slot.maxPeople)
    throw new ApiError(status.BAD_REQUEST, `No seats available`);

  // map through the payload and create bookings to save
  const bookingData = [];
  data.map((obj) => {
    validateFields(obj, ["bookingFor", "moreInfo"]);

    if (!obj.moreInfo.length)
      throw new ApiError(status.BAD_REQUEST, "moreInfo can't be empty");

    bookingData.push({
      user: userId,
      host: event.host,
      event: eventId,
      eventSlot: slotId,
      startDateTime: event.startDateTime,
      endDateTime: event.endDateTime,
      price: payload.price,
      numOfPeople: 1,
      bookingFor: obj.bookingFor,
      moreInfo: obj.moreInfo || null,
    });
  });

  try {
    const bookings = await Booking.create(bookingData, { session });

    console.log(bookings);

    await session.commitTransaction();

    return bookings;
  } catch (error) {
    await session.abortTransaction();
    throw new ApiError(status.BAD_REQUEST, error.message);
  } finally {
    session.endSession();
  }
};

Given transaction number 1 does not match any in-progress transactions. The active transaction number is -1

Given transaction number 4 does not match any in-progress transactions. The active transaction number is 4

Given transaction number 5 does not match any in-progress transactions. The active transaction number is 5

Given transaction number 48 does not match any in-progress transactions. The active transaction number is 47