AWS DynamoDB Pricing Clarification
I would like to use AWS DynamoDB for my project and would like to see clarifications on the following. As part of AWS free tier for DynamoDB, I am entitled to 25GB of storage along with 25 WCU and 25 RCU.
I am quite confused with the terms WCU and RCU.
What I understand 1 WCU represents 1 KB write/second 1 RCU represents 4 KB read/second
What I want to clarify
- If I have a 50KB data, with 25 WCU (explicitly stated when creating the table to stay within the free tier), it will take ~2 seconds to successfully write the data to the table?
- If I cap my table at 25 WCU, writing large size data to my DB will be slow but still within the free plan?
- Does AWS charges for exporting data in DynamoDB to CSV? What are the charges that apply
- WCU and RCU is just AWS way of saying the read and write speed?
- If I have a 50KB data, with 25 WCU (explicitly stated when creating the table to stay within the free tier), it will take ~2 seconds to successfully write the data to the table?
Not quite, DynamoDB will not split the load for you like that. DynamoDB uses burst capacity, which in short is any unused capacity for a 300 second sliding window is banked. So when a your first request comes in, it will consume 50 WCU (25 WCU from provisioned capacity, 25 WCU from your burst bucket), all of which are free tier. When you deplete your burst bucket, DynamoDB will throttle any requests trying to insert data. Then the SDK will retry, eventually succeeding when the burst bucket has accumulated 25 WCU.
- If I cap my table at 25 WCU, writing large size data to my DB will be slow but still within the free plan?
It will not be slow, but it could cause throttling as mentioned above, which cause you to retry. That may add 10's of milliseconds to a write.
- Does AWS charges for exporting data in DynamoDB to CSV? What are the charges that apply
Yes, export charges at $0.10 per GB in us-east-1 and S3 charges will also apply
- WCU and RCU is just AWS way of saying the read and write speed?
Correct