How to perform backward pagination in cognito userpool - node.js

Question

I am working with nodeJs - AWS lambda function, cognito userpool(AWS).
The requirement is of adding pagination feature, for that I am able to perform forward pagination with the help of https://docs.aws.amazon.com/cognito-user-identity-pools/latest/APIReference/API_ListUsers.html,
but I am not able to find, what are the necessary steps to perform backward pagination, so that in UI, the users can scroll to previous and next pages without any issues using the endpoint created by me.
Can anyone help me into this?

Answer 1

Since you are directly accessing cognito API to do pagination for users,
What I would suggest is to pass a paginator value from UI to your API, that API will process your pagination in a loop,
For Example:
For the ease of understanding I will use pagination from 1
and each page is having 8 items,
So let's say,
You are sending querystringparameters something like this:
[your-api-endpoint]?page=1
Now, there is a variable counter which is the number of times your loop will execute,
Start a loop and in that loop call the Cognito API along with token handling capability, so if you call it 1 time you will have first 8 items.
Now let's take another scenario:
You are sending querystringparameters something like this:
[your-api-endpoint]?page=2
Now, the variable counter which is the number of times your loop will execute is set to 2,
Start a loop and in that loop call the Cognito API along with token handling capability, so if you call it you will have first 8 items, and loop will execute one more time since counter is set to 2, therefore you will have next 8 items and you can return that.
In this way your pagination will depend on input from front-end.

Answer 2

Since, I cannot found any specific sdk or code to implement backward pagination in cognito user pool, I have taken help of front end to store the pagination token sent from backend and fetch data accordingly.
So the scenario will be : For first time calling the API, the pagination token value(in headers/or the place where it is kept(params/body/headers)) will be NULL, and response will get a paginationtoken to move to next page, it can be stored in UI code, and use it to move to next page, again response will receive a paginationtoken, store it and proceed further to fetch next page data.
In order to move back to the previous page, use the stored pagination token and fetch the details accordingly.