How to create Global Secondary Index in DynamoDB


Watch my YouTube video for explanation :


Please look into the class notes here for your references:

 Global Secondary Index

Employee Table

EMPID, JOINING_DATE,  LOCATION
1 ,   20-02-2009, Bangalore
2,    12-03-2009, Mysore
3,    31-01-2018, Delhi
4,    27-02-2014, Gurugram
5,    19-04-2008, Pune
6,    18-07-2004, Bangalore

Partition Key   = EMPID
Sort Key     = JOINING_DATE
other attribute = LOCATION
  
Query  Find out all EMPIDs whose location is Bangalore?
  
Approach 1   SCAN operation Filter Expression (LOCATION=='Bangalore') 
Approach 2   Create a GSI , and with index name - lookup the data where LOCATION =='Bangalore' 
   
Meaning of Creating GSI -
        a. Create a new GSI Index meaning define a new partition key
b. when we create a GSI then we create a new table with New Partition Key but keeping these 2 tables in sync
 


LOCATION , JOINING_DATE, EMPID
Bangalore, 20-02-2009, 1
Mysore, 12-03-2009, 2
Delhi, 31-01-2018, 3
Gurugram, 27-02-2014, 4
Pune, 19-04-2008, 5
Bangalore, 18-07-2004, 6

Partition Key = LOCATION
Sort Key = JOINING_DATE
other attribute = EMPID

How the GSI works internally-
GSI partition key requires uniform data distribution, meaning it works best when data is uniformed
Define RCU and WCU separately on the Index
Throttling


Overhead -
   Cost will go higher as the no of GSI index increases , may go up to 20 GSIs
   No guarantees of data consistency
   Need to Keep WCU of GSI table>= WCU of Main Table
   Separate metrices on your GSI for monitoring and action

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