Fast Is Not Enough: Building Apps That Keep Users Coming Back

From fintech to healthcare to live streaming, a mobile product architect and startup growth mentor shares how thoughtful engineering turns first users into loyal advocates.

Most startups pour their energy into getting new users through the door. Ads, launch campaigns, social media buzz — all focused on acquisition. But in reality, growth rarely comes from the first download. Products take off when the people who try them once keep coming back, making the app a part of their daily rhythm.

The difference between a one‑time download and a loyal user often lies in the small, invisible things: how quickly the app responds, whether it feels reliable, and whether it genuinely solves a problem in the user’s life. Founders who focus only on the top of the funnel often miss this: the quiet work of building trust and habit is what drives sustainable growth, considers Artemii Shlesberg, a seasoned expert in mobile product architecture and user‑focused app development.

He was the founding iOS developer and mobile team lead for Voices, a venture‑backed live‑streaming platform built for real‑time interaction between creators and audiences, supporting multi‑channel payments and high‑load video rooms. As an iOS developer and later team lead for the internal startup of a leading Russian digital bank, he built a secure B2B banking application with modular architecture and bank‑level encryption.

In healthcare, he served as the independent developer of ShiftSwap for Yale Hospital, part of the Yale School of Medicine’s emergency residency program, creating a specialized scheduling app that simplified shift swaps for medical staff. Beyond his development work, Artemii has been a judge and winner at major industry hackathons backed by leading tech companies, sharing his expertise with the next generation of builders.

In this conversation, he shares how thoughtful product and engineering decisions turn first users into long‑term growth.

Artemii, as retention and engagement drive real growth, from what you’ve seen, what are the most common mistakes that cause users to leave a product after the first try?

One of the biggest mistakes I see is overloading first‑time users with complexity. Many apps try to showcase every feature right away, but that only creates confusion. Another common issue is a weak first‑run experience — if onboarding is slow, unclear, or requires too much effort, people leave before they see the value.

I’ve also noticed that products sometimes focus more on visual polish than on core reliability. Even a beautifully designed app can lose a user if the first interaction feels clumsy or breaks unexpectedly. In the very beginning, your product has only a few seconds to earn trust, so removing friction and guiding users to their first small win is critical.

How do you approach those very first months of a new product — when there are almost no users yet, but every decision can shape retention and growth later on?

The earliest stage is all about learning, not scaling. When you only have a handful of users, you can talk to every one of them, watch how they interact with the product, and catch friction before it multiplies. My goal is always to get a working prototype into their hands quickly, even if it’s imperfect, and start collecting both feedback and behavior data.

I also think a lot about flexibility in those first months. You don’t know yet which feature will become the core of the product, so the architecture and the team workflow need to support fast iteration without creating long‑term debt. This mindset — listen, learn, adjust — is what guided me later at Voices, where every week of iteration brought us closer to a product users wanted to return to.

Your early work at Voices helped the app grow from zero to 10,000 monthly users in just six months. What were the key product or engineering decisions that enabled that rapid traction?

We treated the first six months as a learning race, not just a coding sprint. From day one, I built the iOS app on Swift with Combine and MVVM, and for streaming we used WebSockets and Agora SDK. That gave us a modular and reactive architecture — we could ship a new build every week and test ideas almost in real time.

On the product side, we focused on interaction, not just passive viewing. Live rooms where creators could see and respond to their audience instantly became our core feature. Once users felt heard, they kept coming back, and word of mouth started to work for us.

As the mobile team lead, you introduced multi‑channel monetization with Apple Pay, Stripe, and crypto/NFT donations. How did you ensure the payment experience felt seamless for users while meaningfully boosting revenue?

I think of monetization as part of the user experience, not an afterthought. People want to support creators, but if you add friction like too many steps, logins, or slow loading screens, you lose them.

I worked with our CTO to build a flexible payment module that handled Apple Pay, Stripe, and crypto wallets natively. It ran quietly in the background, so donating or validating an NFT felt like tapping a like button. Once payments felt effortless, revenue grew month over month, and we saw a direct correlation: the smoother the UX, the higher the engagement and the more creators earned.

After working on live‑streaming apps with rapid user feedback, you also tackled a very different challenge — hospital shift management. What drew your attention to this problem, and how did understanding the residents’ pain points influence the way you built ShiftSwap?

When my wife began her medical residency, I noticed how inefficient shift-swapping was — done through emails and spreadsheets, it caused delays, errors, and unnecessary stress. I saw an opportunity to help and, without initial support from the program, began developing ShiftSwap. I spoke with residents and administrators, mapped out the compliance rules, and designed a simple app tailored to their needs.

The result was a tool that reduced swap turnaround from days to hours and reached over 90% adoption in the program. It improved not just scheduling, but also morale and work-life balance. For me, it proved how deeply understanding users’ pain points, especially in high-stakes environments, can lead to meaningful, lasting impact.

From solving operational challenges in healthcare, you also explored the emotional side of user experience with the experimental Magic Mirror project. What did this experiment teach you about building apps that connect with people on a deeper level?

Magic Mirror was all about human connection. We wanted to see if a phone could create a sense of physical presence across distance, not just a video call. The project taught me that emotion lives in the details, like a slight delay, an awkward interface, or a cold design breaks the illusion instantly.

Even in startups, this lesson holds. A product that resonates emotionally will create stronger engagement and retention than one that’s merely functional. Whether it’s fintech or streaming, if a user feels understood, confident, and connected, they’re far more likely to return and to recommend the app to others.

Your projects range from highly practical to deeply experimental. At the same time, you’ve stayed close to the startup and developer community through major hackathons. How have these experiences influenced the way you approach building and evaluating new products?

Hackathons are like product boot camps. You see teams under pressure, solving problems with limited time and resources. As a judge, I learned to spot clarity and focus immediately — the best teams don’t try to build everything; they solve one pain point in a way that feels inevitable.

That mindset stays with me. Even in long-term projects, I ask: what’s the smallest thing we can ship that proves the value? Hackathons also keep me humble — there’s always a new idea or approach that makes you rethink your assumptions.

Looking back at your experience — from fintech to live streaming to hospital apps — what would you say is the single most important factor for turning early users into long-term adopters?

It always comes down to trust. Trust that the app will do what it promises, that their data is safe, and that their time isn’t being wasted. In fintech, trust comes from security and reliability; in live streaming, it comes from performance and smooth interaction; in healthcare, it’s about clarity and dependability. Once users feel that your product is a reliable part of their routine, retention almost takes care of itself.

Many founders focus on rapid acquisition, but your work shows that sustainable growth comes from retention and user trust. If you could give one piece of advice to a startup team planning its first product launch, what would it be?

Start by solving one real problem for a small group of users, and solve it so well that they can’t imagine going back. Fancy features or marketing campaigns won’t save a product that doesn’t deliver value from day one. If those first users trust you and love the experience, they’ll become your advocates and that’s the fastest and most sustainable growth a startup can have.