AWS Free tier Read/Write allowance/table

Question

AWS Free tier allows 25 Read/Write per account. I am not able to understand how this is allotted.

I tried with MAX 8 Tables and MIN 2 Tables (Single DB only). AWS is allotting 3 Read/Write per table no matter what are the number of tables in DB. (I didn't go above 8 as it might cost me for going above the allowance of 25 R/W (not sure)).

Can someone clarify if I make only 2 tables for my DB,can I increase my R/W limit for each to 12? There is an option to do that, but it results in an increase in price (Services -> DynamoDB -> Tables -> Choose Table ->Capacity).

Answer 1

As Per Amazon DynamoDB Pricing :

Free Tier*

As part of AWS’s Free Tier, AWS customers can get started with Amazon DynamoDB for free. DynamoDB customers get 25 GB of free storage, as well as up to 25 write capacity units and 25 read capacity units of ongoing throughput capacity (enough throughput to handle up to 200 million requests per month) and 2.5 million read requests from DynamoDB Streams for free.

Now, Let's See What is ReadCapacityUnits & WriteCapacityUnits ?

As Per DynamoDB Documentation For Working With Tables :

ReadCapacityUnits

One Read Capacity Unit = one strongly consistent read per second, or two eventually consistent reads per second, for items up to 4 KB in size.

WriteCapacityUnits

One write capacity unit = one write per second, for items up to 1 KB in size.

Calculating ReadCapacityUnits / WriteCapacityUnits

First, you need to calculate how many writes and reads per second you need.

1 million evenly spread writes per day = 1,000,000 (No Of Writes) / 24 (Hours) / 60 (Minutes) / 60 (Seconds) = 11.6 writes per second.

A DynamoDB Write Capacity Unit can handle 1 write per second

So you need 12 Write Capacity Units.

Similarly, to handle 1 million strongly consistent reads per day, you need 12 Read Capacity Units.

Summary : You have a Big Pandora's Box as a Free tier. If you haven’t used up your free tier allotment (25 write capacity units, 25 read capacity units, 2.5 million Streams read requests, 25 GB of storage), you can run this application for free on DynamoDB.