Research AWS pricing

[davidtaing]

DynamoDB

• https://aws.amazon.com/dynamodb/pricing/on-demand/
• https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/read-write-operations.html
• https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/transaction-apis.html

Notes:

Units

• 1/2 RCU per 1KB (consistent reads)
• 1RCU per 4KB (consistent reads)
• 1WCU per 1KB

Query Operations

• GetItem - each item gets rounded up to nearest boundary.
• BatchGetItem - each item gets rounded up to the nearest boundary. I assume this is a single network hop, so it may be cheaper in terms of compute.
• Query - gets multiple items with the same partition key. Results are treated as one read but there is a maximum of 1 MB of data.
• Scan - reads entire table. See Working with scans in DynamoDB for further info.

Mutation Operations

• PutItem - larger of previous / new item
• UpdateItem - larger of previous / new item
• DeleteItem - size of the item deleted
• BatchWriteItem - each item is rounded up to the nearest boundary

Transaction Operations

• Doubles the RCUs / WCUs

See: Capacity management for transactions

Comments

• Generally each item gets rounded up to nearest boundary. Only Query buckets items as a single read.
• Use Query over BatchGetItem when fetching items with the same partition key****