Instacart: A Case Study in Conflicting Needs

See how our UX Designer uses usability heuristics to evaluate popular grocery-delivery service, Instacart.

by Andrew Croce

Recently, I made a mistake when shopping on Instacart. I did it a couple of times actually.

Some background

I have a two-year-old son who, like a lot of toddlers, is addicted to milk. In an effort to begin weaning him off the stuff, we recently decided to switch from whole milk to 2% milk. Simple enough - from now on we just buy the turquoise-colored cap, instead of the red one.

So what's the error? We'll come back to that later.

A pressing need for adoption

I started using the Instacart mobile application during the 2020 lockdown. It addressed an immediate need that had to be solved. I (along with millions of others) could not physically enter a grocery store during a pandemic, and I needed to get groceries or my family would not eat.

Prior to this, we had never used a grocery delivery service. Using Instacart was an obvious solution, and despite some initial bugs and delays, we persisted in using it weekly.

Successful staying power

Even after the lockdown was lifted, we continued to use Instacart. Why? The app solves a previously unknown need: it saves us time by allowing us to be home or working while our groceries are picked and delivered. We had never truly considered the actual cost of our time spent grocery shopping, and it quickly became obvious that the cost of delivery was outweighed by the time savings.

While this was not our initial, primary reason for using Instacart, it has become the reason we continue to use it.

Has it won my loyalty?

Sort of, but the jury is still out. Does this product build enough satisfaction that I'd reject another product? So far, yes, but nothing has yet posed a viable alternative. We continue to use Instacart because of lack of competition (Shipt, for example, doesn't cover our favorite stores), and — let's be honest — inertia: it's easier to stick with what we know.

Evaluating my error

Let's get back to the milk story: in making the switch from whole milk to 2% milk, I had to do a little bit of remembering for a while. When purchasing milk, I needed a mental assist to remind me to get the turquoise cap, not the red.

Fortunately, while physically in the grocery store, the strong visual signifier of color serves that purpose well (for color-sighted people, anyway). Lined up in the refrigerator cases are all the varied colors of milk packaging. It's easy to quickly grab the milk I always get, but it's also easy for me to see those varied colors standing out, effectively jogging my memory about getting the new one.

An efficiency feature made me forget

When using Instacart, however, adding things to your virtual cart is often much quicker and easier than doing it physically, in the store. This is usually a good thing. The app remembers what I purchase frequently, and the user interface presents shortcuts to these items so I can quickly add them with one tap.

I did that with the milk a few times. The red milk.

I bought whole milk without even thinking about it. I did not have the same real-world colored-cap context to act as a reminder. Instacart's shortcut feature short circuited my long term memory.

The relevant heuristics

There are a number of well cited usability heuristics that are used to help designers understand the reasons why errors occur. These heuristics are rules of thumb derived from long standing human-factors research and practitioner experience. The most commonly cited list of usability heuristics comes from Jakob Nielsen; while not necessarily comprehensive or definitive, it's still a good place to start.

Nielsen's second heuristic calls for a "match between system and the real world". It states:

"When a design’s controls follow real-world conventions and correspond to desired outcomes ... it’s easier for users to learn and remember how the interface works. This helps to build an experience that feels intuitive."

Years of experience shuffling around grocery stores has ingrained in shoppers' minds certain patterns of decision making. The ability to see all the choices in front of you, while certainly time consuming and sometimes paralyzing, can also be very useful. Comparing items is completely intuitive in a physical store; just pick up the items and compare.

Conflicting user needs

In Instacart's mobile app, comparing products is hard. Their design prioritizes the user need for time-savings over the need for choice-support. In solving one genuine problem of slow, inefficient shopping, Instacart created another little problem that might occur when people need to change their habits. People usually buy the same things over and over, but not always. Instacart arguably leaned a little too hard on a different heuristic: "Flexibility and efficiency of use" which states:

"Shortcuts ... may speed up the interaction for the expert user such that the design can cater to both inexperienced and experienced users."

Indeed this shortcut feature does speed up the interaction for most repeat users, but at the expense of possibly undermining a different, unmet need and, at times, diminishing the user experience.

My goal here is not to bash Instacart; as I said, we still use this app regularly and it has saved my family a lot of time. Rather, my goal is to point out the genuine challenge of prioritizing user needs in product design.

Instacart could design and implement features that address my habit-switching need — but I will not say they could do so easily.

Perhaps, as the use of their product has skyrocketed in the last year, they're only just now learning about the less prominent use cases that give some people headaches. Perhaps they're currently performing user research to learn from the behaviors of in-store and in-app shoppers. Perhaps their UX team is iterating on different design solutions that seamlessly mesh a variety of use cases.

Perhaps it's in the next update.

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