Optimistic locking when working via REST API

Question

I have a case when SF data can be updated concurrently by humans with UI and by a Ruby app via REST API, so I'm worried about the possibility they overwrite changes of each other.

Is there a standard way to conditionally make an update only if the object hasn't been changed in the meanwhile?(check the version of object, or last update time, etc).

Or is it possible to achieve this with a SOQL query similar to this?
update stuff set calculated_field = 'new value' where base_field = 'expected old value'

Answer 1

If the Ruby script updates a record between the time the user loads the edit page and clicks Save, they'll get a "record has been modified" error to prevent them from overwriting data.

If the user updates a record between the time the Ruby script queries the record and chooses to update the record, that data may be overwritten unless the Ruby script provides the If-Unmodified-Since header. As a practical matter, you should always use the If-Unmodified-Since header to avoid overwriting data from other sources.

You can also use the If-Match header if you cached the ETag header, which is a hash that defines the state of the record at the time of retrieval. You can also use this to prevent unintentional overwrites to the data by providing the expected hash value.

You can read more about that header, and more, in the Using Conditional Requests documentation.