After speaking with a recruiter, I completed an initial 30 minute screen with a manager, followed by instructions to complete a sample app before being able to move forward. This sample app was basic, yet time consuming (it took me nearly 5 hours). It was not challenging, and did not represent a variety of skill. You're told you have no more than 5 hours to complete it, and I felt quite rushed to do so to the quality I was comfortable with.
The onsite interview was disappointing and not a thoughtful evaluation of skill. I was not asked a single technical question by anyone. Several of the interviewers seemed disinterested from the moment they walked in, and almost all were doing something else while interviewing me on their laptops.
Overall, interviewing with Instacart was a waste of time. The recruiter painted a picture of the company and engineers that was different than what I observed.