Hello @venkatkumar229
Data streams are designed for append-only time-series data so they are not suitable when you need global de-duplication based on _id.
_id uniqueness is enforced only within a single backing index so after rollover the same _id can be indexed again in a new backing index (the same behavior seen in your case)
The same thing happens with regular indices using rollover and a write alias because Elasticsearch does not check older indices for existing _ids.
If you require exactly one document per business key (for example seqId), the recommended approach is to use a Transform or will have to avoid rollover of index (which might not be a feasible solution).
Similar post :
Thanks!!