I am quite new to Amazon DynamoDB. I currently have 20000 rows that I need to add to a table. However, based on what I've read, it seems that I can only write up to 25 rows at a time using BatchWriteItem class with 25 WriteRequests. Is it possible to increase this? How can I write more than 25 rows at a time? It is currently taking about 15 minutes to write all 20000 rows. Thank you.
You can only send up to 25 items in a single BatchWriteItem request, but you can send as many BatchWriteItem requests as you want at one time. Assuming you've provisioned enough write throughput, you should be able to speed things up significantly by splitting those 20k rows between multiple threads/processes/hosts and pushing them to the database in parallel.
It's maybe a bit heavyweight for that small of a dataset, but you can use AWS Data Pipeline to ingest data from S3. It basically automates the process of creating a Hadoop cluster to suck down your data from S3 and send it to DynamoDB in a bunch of parallel BatchWriteItem requests.