Threshold of Document size and numbers in Transactional Upsert and alternatives via MongoDB .NET

Working with Data
,
1

I need to insert or update multiple documents of 150,000+, total in size of 20+ MB atomically using MongoDB Transaction.

var client = new MongoClient(ConnectionString);
using (var session = await client.StartSessionAsync())
{
    try
    {
        // execute async operations using the session          
            var database = client.GetDatabase(DatabaseName);

            var carCollection = database.GetCollection<Car>(CarName);
            var writeModels = new List<WriteModel<Car>>();

            foreach (var item in Cars)
            {
                var filter = Builders<Car>.Filter...;
               
                var update = Builders<Car>.Update...

                var upsert = new UpdateOneModel<Car>(filter, update) { IsUpsert = true };
                writeModels.Add(upsert);
            }
            await carCollection .BulkWriteAsync(writeModels);
    }
    catch
    {
        await session.AbortTransactionAsync(); // now Dispose on the session has nothing to do and won't block
        throw;
    }
    await session.CommitTransactionAsync();
}

MongoDB imposes a max limit of 100,000 document on each batch, and 16MB in size, if I remember correctly,

Question

How to get around the limitation of the batch update.

https://mongodb.github.io/mongo-csharp-driver/2.13/reference/driver/crud/sessions_and_transactions/