when I first started NetSuite RESt APi could not handle many things where is it holding now? we are looking to upgrade our current application that uses soap API

FWIW, I wouldn't necessarily call switching from SOAP as an 'upgrade'

can you explain what you mean ?

unless you're doing something with the REST API that you couldn't do with SOAP or where REST is significantly faster I'd argue it's not an 'upgrade' in the sense that 'upgrade' = 'improvement'.

We have been using REST API to handle most of our record changes and creation. The limitations we ran into was linking records and pulling in the associated data. For those instances we created a function on our separated backend that gathers up all the data and presents it in a better JSON format(ie, for a Sales Order we want to pull in all the fulfillments, and packages associated with it.) This custom function uses a combination of the REST api and SuiteQL queries to associate data. We were hesitant at first but for our use case, we can make it work.

sorry for the distraction - Eric's reply answers the original question exactly.

No problem! We are spoiled by Eric's contributions to the NetSuite community!