Nightly process for a dataset of 150k entries

I recommend using Appian's synced record type feature to accomplish this easily 

https://docs.appian.com/suite/help/21.4/configure-record-data-source.html#web-service

You can set up the record type to sync every night at a specific time.

Typically you'd get the data, load it to a "staging table" in its raw, unchanged form (so that you can decouple the receiving of the data from the subsequent processing). Once it's in a staging table you can then process it in small batches so that you don't create a memory spike in your environment. 

There is the "Transaction Manager" application in the the AppMarket that is specifically designed to manage queues of work, to provide multi-queue processing and throttling of the transactions, and other patterns that you'd typically want in this type of scenario.