Jmeter Performance Testing - Difference in result count get from API and from MongoDb

I have created a performance test suit using JMETER 4.0 and i have multiple test cases which are divided in 2 fragment and i am calling them from a single thread. Following are the type of test cases which are in 2 fragments.

Test Fragment 1: CURD operation on User

Test Fragment 2: Getting User counts from MongoDB and API's and comparing them and test cases from Test Fragment 1 runs first multiple time based on thread count and then test case from second fragment runs

In Test Fragment 2 i am having these two test cases

TC1: Fetching user count from mongoDB(using JSR223 Sampler)

TC2: Fetching user count using API

When 2nd Test Fragment runs then test case to fetch user count from mongoDb gives different count compared to test case which fetch count using API directly. API's are talking time to update data in mongoDB as there could be some layers which takes time to update data in database(i am not sure which layer exists and why it takes time exactly). The Scripts work fine when i run it for single user so there is not doubt that something is wrong with script.

someone please suggest what approach we can use here to get the same count.

a. Is it a good approach to add timers/delay or something else can be used?

b. If use use timer/delay is it effects performance test report as well, are those delays going to add up in our performance test reports?