Hello Sanyal, Mihir,
Welcome to the MS Q&A platform.
Since you are using Azure Data Explorer (ADX) for big data analytics, you can leverage its native features for imputing missing data. ADX provides native functions for time series analysis and data manipulation, including interpolation and extrapolation functions that can be used to impute missing values
Regarding your question about whether to impute the data before ingestion into ADX or in ADX itself, it is generally recommended to impute the data before ingestion if possible, as this can reduce the amount of data that needs to be ingested and can improve query performance. However, if the missing data is spread out over a long period of time, it may be more efficient to impute the data in ADX using the native features.
Regarding cost considerations, imputing the data before ingestion may be more cost-effective, as it can reduce the amount of data that needs to be ingested. However, this depends on the specifics of your use case, and you may want to consider the cost of storage and query performance in addition to the cost of ingestion.
I hope this helps. Please let us know if you have any further questions