Amazon DynamoDB is a NoSQL transactional database that provides single-digit millisecond latency even at petabytes scale. This Amazon Web Services (AWS) serverless offering is getting popular because of its consistent performance and scalability. You do not need to provision underlying infrastructure. Your single table can grow up to petabytes.
With on-demand capacity mode, you pay per request for the data reads and writes that your application performs on the tables. AWS charges are based on the accumulated read request units (RRUs) and write request units (WRUs) in a month. DynamoDB monitors the size of your table continuously throughout the month to determine your storage charges. It supports continuous backup with point-in-time-recovery (PITR). DynamoDB monitors the size of your PITR-enabled tables continuously throughout the month to determine your backup charges.
To estimate the DynamoDB cost for a project, it’s important to calculate how much RRU, WRU, and storage will be consumed at different stages of your product lifecycle. For a rough cost estimation, you can use AWS Pricing Calculator, but you must provide an approximate number of RRUs, WRUs, and storage requirements for your table. These can be difficult to estimate at the beginning of the project. AWS Pricing Calculator doesn’t consider data growth rate or item size, and it doesn’t consider the number of reads and writes for the base table and global secondary indexes (GSIs) separately. To use AWS Pricing Calculator, you must estimate all those aspects to assume ballpark figures for WRU, RRU, and storage size to obtain your cost estimation.
This pattern provides a mechanism and a re-usable Microsoft Excel template to estimate basic DynamoDB cost factors, such as write, read, storage, backup and recovery cost, for on-demand capacity mode. It is more granular than AWS Pricing Calculator, and it considers base table and GSIs requirements independently. It also considers the monthly item data growth rate and forecasts costs for three years.
