Calculate required read throughput for AWS DynamoDB

calculate-dynamodb-read-throughput.js

/**
 * [calculate description]
 * @method calculate
 * @param  {Number}  itemsCount            number of items to be read
 * @param  {Number}  itemsRequiredTimeRead required time in seconds to read those items
 * @param  {Number}  itemSize              the size of each item in KB
 * @param  {Boolean} isStrongRead          the consistency model of Read : Strong or eventual
 * @return {Number}                         Read throughput
 */
function calculate({itemsCount, itemsRequiredTimeRead, itemSize}, isStrongRead = true) {
  const READ_UNIT  = 4 ;//kb
  const itemsPerSecond = itemsCount/itemsRequiredTimeRead;
  const itemReadUnits =  Math.ceil(itemSize / READ_UNIT)
  const readThroughput =  itemReadUnits * itemsPerSecond;
  return  Math.ceil(isStrongRead ? readThroughput : (readThroughput/2));
}

module.exports = calculate

sample-calculate-throughput.js

const calculateReadThroughput = require('./calculate-dynamodb-read-throughput'); 

/**
* -- Example 1--
You have an application that requires to read 10 items of 6kB per second using eventual consistency. 
What should you set the read throughput to ? 

-- Analysis 
itemsCount = 10 
itemsRequiredTimeRead =  1 second (per second)
itemSize = 6 (6kB)
isStrongRead = false (Eventual consistency)


-- Solution
*/
calculateReadThroughput({itemsCount: 10, itemsRequiredTimeRead : 1, itemSize: 6}, false)
// RESULT : 10 units of read throughput

/*****************************************
* -- Example 2--
You have a motion sensor which reads 1200 items of data every minute. 
Each item consists of 5kb. Your application uses eventually consistent reads.
What should you set the read throughput to?

-- Analysis 
itemsCount = 1200 
itemsRequiredTimeRead =  60 second (evey minute = evey 60 seconds)
itemSize = 5 (5kB)
isStrongRead = false (Eventual consistency)


-- Solution
*/
calculateReadThroughput({itemsCount: 1200, itemsRequiredTimeRead : 60, itemSize: 5}, false)
// RESULT : 20 units of read throughput