On-demand reads, writes and storage for a DynamoDB table.
DynamoDB write units cost about five times a read unit, so batching, condensing items and avoiding hot-key rewrites saves real money. For steady traffic compare with a relational option on the managed database cost calculator.
Free DynamoDB cost calculator — monthly reads, writes and stored data to your real on-demand table bill.
On-demand charges per million read request units (about $0.25) and per million write request units (about $1.25) — writes cost roughly 5x reads. Storage is about $0.25 per GB-month after a 25GB free tier.
On-demand is simplest and great for spiky or unpredictable traffic. If your read/write rate is steady, provisioned capacity (optionally with auto-scaling and reserved capacity) can be substantially cheaper per request.