The Design Principles Of The POS System · POS Design Guide Part 2
Last Updated: May 12, 2023
In part I, we dealt with UX design challenges that apply to POS interfaces. Moving on, we’ll be summarizing the design principles that emerge from the data we gathered through on-site user research assignments, our lab experiments, and the POS designs we created for our customers.
These POS design principles complement the design industry’s general UX principles. They offer insight on best practices employed to deliver POS user interfaces that work in real-life.
POS User Interface Design = Ergonomics
This apparent no-brainer masks the difficulty of reconciling aesthetics and usability in a POS interface.
The battle between usable and pleasant to look at when designing a POS interface is fierce. Many of the legacy systems look horrifying, but people who got used to them appreciate certain quirks that work as shortcuts. It is critical for designers to discover all these quirks and understand them. Further on, they must figure out the underlying ergonomic principles in order to apply them in a manner that is contemporary in feel and facilitates the overall aesthetic of the interface.
Throughout our research, we have documented many shortcuts and interactions that are truly hideous, but work. By studying why they are useful to cashiers, we have been able to beautifully integrate them into the contemporary interfaces we have created for POS providers.
Design for Hours of Use
A POS user interface has to be designed for two very different scenarios: newbies who are confronted with too much information (cashiers come and go), and power users who will execute the same interaction millions of times.
Good luck balancing those trade-offs…
Designing for a POS interface is sort of like packing for climbing a mountain: anything that seems light on the ground will feel 10x heavier after half a day of hiking. In a POS interface, every minor inconvenient step in a UX flow will make thousands of interactions more difficult every day.
Design Patterns Are a Double-Edged Sword
Designers of websites or mobile apps can often rely on design patterns to solve usability issues to a mediocre (but sufficient) level. However, in the design of POS interfaces, you can’t get away with that because the same design patterns rarely apply to a POS system, for reasons outlined in the first part of our series on POS design.
Deciding whether to use a design pattern or not requires the team to carefully balance the needs of all stakeholders and the specific challenges they are trying to overcome. Sometimes, a design pattern that seems to work will have significant adverse effects in the broader context of the user experience. Designers must understand that POS are used the same way as a standard tablet app, and users may end up doing completely different things than what the designer intended.
Updates Are Difficult
Most apps get updated often, and even when users feel odd at first, they adapt easily. Providers can iterate and change a lot, gradually shifting from MVP to a refined product.
Updating a POS interface is more challenging, because after 2–3 weeks of using the interface for hours each day, cashiers become familiar with the interface through conditioning. Undoing these automated gestures is difficult and requires conscious override. This introduces a big challenge to cashiers, who already have to deal with a lot of other stress factors in their work. Cashiers have to be able to rely on the system without making an added effort to interact with it.
Create Order Out Of Chaos
The POS interface has to ensure that cashiers work according to accounting rules and cope with the unpredictable and surprising nature of reality in a retail facility. Often times, these imperatives are contradictory and very difficult to reconcile.
The role of the designer is to create a framework where these clashing needs can converge in an interaction that is best for all. Coherence and a sound logic beat superficial fixes that only complicate the user experience. Such “fixes” lead to more errors, resulting in a scenario that makes the user’s life difficult and produces erroneous accounting outcomes.
Use Visual Representation Wisely
Most inexperienced designers would improve a legacy POS software interface by adding product images and icons. However, there’s an ongoing debate about the (many!) pros and cons of this practice.
What’s missing from POS software is not the visual element, but the understanding of how users achieve outcomes in the daily use of the POS. Therefore, designers have to attend to a deep understanding of that reality first, and add visuals only in the final stages. POS software has to be designed to work in unison with the cashiers’ mind.
Visuals are not the shortcut that’s missing.
Create Interactions, Not Buttons
The classical paradigm of POS user interfaces is adding a button for every task. Best to have it in there…
Contemporary trends are all about removing buttons and hiding them. However, our user research shows that both of these approaches are wrong because they neglect the reality of how users engage with a POS interface.
Cashiers don’t care about buttons: their existence or lack thereof can be equally problematic. However, cashiers care about meaningful interactions that are finely tuned to how they work.
Design For Simplicity, Step By Step
Tapping is another red herring. Both legacy POS interfaces and contemporary POS interface providers got it wrong, according to the tests we performed. Cashiers can be incredibly fast at tapping, as long as interactions make sense. POS ergonomics means understanding the capabilities of cashiers and how they evolve, in order to design interactions which support them and provide fall-backs when they fail.
Process steps must be designed so as to balance cognitive load. Legacy systems often have a high cognitive load, due to interfaces with a lot of options and few interaction steps, while most contemporary POS interfaces increase cognitive load due to a labyrinth of steps. Designers must take what is best from both systems and blend simplicity with logic.
The Tricky Case of Customization
Customization can be a great idea, but it can also create problems. It has to be deployed very mindfully, taking into account that too much customization can lead to problems, such as consistency across business points, unhealthy work habits, and exploitation of weaknesses to defraud the retailer.
One should be mindful that some people will apply customization where allowed, and then disappear from the organization. Others will use that customization as a given in the interface. This is how the option to customize the interface may lead to a reduced level of usability in the long term.
Customization should be applied sparingly, and only when it fits into the larger user experience paradigm that is emulates the needs of the cashiers and the business.
Understand the Hardware
Hardware components and their limitations are important in human-computer interaction, but designers of web apps and mobile apps get away with almost anything because the hardware they design for does not offer much room for surprise.
POS systems are different: each provider has a different hardware solution, with display peculiarities and connectivity issues. While most POS providers aspire to offer a universal solution, this cannot be truly reconciled with a proficient user interface, because a POS user interface must include many tough choices.
Adding “works on any kind of tablet” as a requirement is akin to deciding to have a low value interface that is (hopefully) compensated by more adaptability. This is yet another trade-off that the designer must be aware of.
Lend a Helping Hand to Users
There are very specific processes where users of POS interfaces run into trouble. They result from the general way of using a POS, as well as from business particularities.
Finding solutions for these key interactions has a significant impact on their daily routine and their well-being. It also makes training easier, because the central part of training is practicing how to do difficult things.
Conversely, certain tasks are so easy for cashiers that they do not require further assistance.
Thanks to the user studies we did in real retail locations, where we observed dozens of users, we discovered many different shortcuts and hacks cashiers use to do their job better.
Many of them have been insightful, and inspired original interactions we have created in POS interface designs. This is the big picture: different users prefer to do things in different ways. Rather than designing a software interface that is rigid and forces users to do things a certain way, the interface should be designed in a flexible way, so different people can find different ways of achieving their outcomes.
The Healthy Dose of Validation
The key principle of providing user-feedback in regards to the results of their actions applies to POS systems, but designers must approach it in a more nuanced way.
Validations pose a challenge. Soon enough, they might become obsolete and be perceived as a hindrance to users who would be much faster if they didn’t have to hide messages.
POS software interfaces present a unique set of use cases and of complicating factors. When designing a POS user experience, the general principles of human-computer interaction must be augmented by these additional principles, which add nuance to the design process.
The principles we have outlined are based on the numerous user studies we have conducted on cashiers in real retail locations, a lab test on current POS systems, and our own work in designing for POS providers.
If you are interested in more UX case studies, check out The Border Force Goes Digital on our website, https://www.interface-design.co.uk/.
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