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Calculate required read throughput for AWS DynamoDB
/**
* [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
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
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