API - ability to create/update multiple observation field values in one call?

Each call to the API is taking between 1.2 and 2.5 seconds. We are making multiple calls, one to add the observation to the project and one per observation field. This causes a slow response of 10-15 seconds on our user interface.

@carrieseltzer - would it be possible to get some input from an iNaturalist developer on how to improve the performance of updating multiple observation fields?

/cc @jon_sullivan @murray_dawson