Build Fast, Fail Fast, Move Forward: Lessons from Applying Lean Approach in a Growing Startup

"Build fast, fail fast, move forward" — this phrase has almost become a mantra in startup circles. But behind the buzzwords lies a well-grounded philosophy that originates from the assembly lines of Toyota. Developed to streamline production and eliminate waste, the lean thinking and approach to management have since migrated into the heart of the software world.

We didn’t invent lean development, but we’re certainly living it. It’s at the core of our approach to building products and managing teams. In this article, we’ll explore how we practise lean at Rebbix and why it’s such a natural fit for startups. We’ll also walk through a real project where a client came to us as a startup and kept growing with our support.

Why startups thrive with lean approach?

Early-stage companies typically operate with tight resources, fast-changing priorities, and an urgent need to find product–market fit. Many of us have seen the sobering statistics claiming that 80% of startups fail or that only 50% of new businesses make it to their fifth year. And even though some of that research is vague in terms of what ‘failure’ means or based on a limited selection of companies, it goes without saying that the world of startups can often be unforgiving. 

However, according to a report by Startup Genome, based on in-depth research of Silicon Valley companies, those startups that pivot once or twice achieve 3.6 times better user growth and raise 2.5 times more funding than their peers. In contrast, startups that never pivot or pivot more than twice perform significantly worse. What these stats reveal is that the difference between success and failure often isn't the initial idea and requirements — it's how quickly and systematically you can test, learn, adapt, and draw the right conclusions. 

And this is where the lean methodology becomes essential. It offers a structure for the usual startup uncertainty — build the smallest version of a solution, test it, learn from real data, and adjust quickly, without overengineering and overcommitting too early. 

For startups, lean thinking is often the difference between building momentum and burning out.

How we apply lean principles in action: Fixly’s growth story

Theory is good, but let’s move on to how the principles of lean development can be used in practice. For this, we’ll use the example of Fixly (a part of OLX Group) — a Polish service marketplace that connects customers with service providers. 

When we started our collaboration, Fixly had a functioning service marketplace and one app for service providers, but they lacked the systematic approach needed to optimize user experience, validate market assumptions, and scale effectively. Since day one of Rebbix joining forces with Fixly, we have been working with the lean mindset. New features have been introduced as an experiment, assumptions have always been tested, and decisions have been driven by data rather than opinion. Let’s see what we achieved.

Now it’s time to explore which principles of the lean approach helped us reach those targets. 

1. Building a culture of hypothesis-driven experimentation

One of Fixly's first major challenges was optimizing their user acquisition funnel. Rather than making assumptions about what users wanted, our team applied the core lean principle of treating every improvement as a testable hypothesis.

However, the important thing here is to understand that proper experiment design — defining success criteria, establishing measurement frameworks, and clarifying hypotheses — is more important than rushing to implementation. Here’s how our Engineering Manager, Yaroslav Rushchak, explains it.

‍Yaroslav: “Lean is all about minimizing the time from idea to feedback. In Fixly’s case, we ran around seven different experiments just to figure out which login flow had the lowest drop-off. But the key thing is: you define success or failure before you write any code. Otherwise, any stats and numbers can be twisted to say anything. That’s why a lot of work happens before coding even starts — setting expectations, defining metrics. That’s what makes 'fail fast' meaningful, not reckless.”

The login experiments were just the beginning. Before feature rollout, we have also implemented A/B testing and fake door testing (creating placeholder features to gauge user interest before investing in development). This approach allowed Fixly to validate demand for new features with minimal investment, ensuring that development resources were always directed toward functionality users actually wanted.

2. Rapid prototype development with minimal resources

Perhaps the most compelling example of lean thinking in action came when our team was getting ready for a meeting with Fixly’s business division. Instead of arriving with just presentations and promises about meeting objectives, they had something much more powerful: a working prototype of the customer-facing app.

Yaroslav: “When my colleagues were getting ready to travel to Warsaw for a meeting with Fixly’s business team, I had some time on my hands and decided to write a prototype of an app for customers. At that time, Fixly only had the app for the providers to offer their services. I saw an opportunity for growth there and decided to create a prototype of the second mobile app, where customers can describe their needs and place orders for the providers. I got it ready in 2 weeks. When our team arrived for the meeting, they had something to demonstrate — to show that we could do it, and much faster than the stakeholders might have expected.”

This two-week mobile app prototype perfectly embodies the lean principle of building minimum viable products to validate assumptions quickly. Rather than spending months on a full-featured customer app, Yaroslav created just enough functionality to test the core hypothesis: would a dedicated customer app add value to the marketplace?

Yaroslav: “This approach works because we immerse ourselves in the domain we're working in. We understand what's truly needed versus what's just nice-to-have, which allows us to take initiative on projects like this.”

As a result, the prototype helped deepen our future partnership and became the foundation for Fixly's customer-facing platform — a key component in their journey to one million monthly users.

3. Starting small and scaling what works

One of the core principles of lean thinking is to start with a minimum viable solution, validate that it works, and then systematically expand on what's proven successful.

Such incremental scaling isn't about being cautious or lacking ambition, but rather about being strategic with limited resources and reducing the risk of building something nobody wants. As Yaroslav explains, "it's better to write code that's easier to throw away rather than change." This philosophy extends beyond code to entire products and team structures.

Fixly's product journey perfectly illustrates how lean scaling works in practice. The company didn't start by trying to build a comprehensive marketplace with multiple apps and complex integrations. Instead, they began with a focused solution — a single app for service providers — and added the second app for customers only later. 

The same applied to team scaling. We didn’t build the team based on org charts or ambitious projections. We expanded it based on validated need, adding specialists only when the workload and complexity demanded it.

Yaroslav: "We started with around 2 people, then when I joined there were about 10, and we grew from there. The team grew as the amount of work increased. We gradually added people who were needed to do the work and implement the new functionality.”

Here’s the example of how such team scaling may look in practice:

4. Technical debt management and cutting corners

Lean methodology isn't just about building. It's also about knowing when to remove features that aren't working and how to keep everything ‘clean’ by managing technical debt. Working with Fixly, our team made strategic decisions about technical debt based on the company’s stage and needs. For early-stage features, we embraced the philosophy of building things that were easy to discard if something went wrong. Instead of investing significant resources to perfect them from the start, we focused on lightweight solutions — knowing they might never be used or could even introduce new issues. 

Yaroslav: “It’s important to remember that teams need to clean up after themselves by bringing the code to order and cutting unnecessary features down in time. Because those things can pile up and create problems in the future, dragging the project down.”

Summing up

Fixly's transformation from a startup to a stable platform serving over one million monthly users wasn't built on luck or revolutionary ideas. It was the result of systematically applying lean principles that any startup can implement. This case demonstrates that lean methodology is a practical framework for navigating startup uncertainty and achieving sustainable growth.

What makes lean development so powerful for startups isn't the individual techniques, but the mindset shift it represents. Instead of betting everything on assumptions, you build algorithms for rapid learning. Instead of pursuing perfection, you optimize for speed and adaptability. Instead of scaling prematurely, you grow based on validated demand. This approach alone doesn't guarantee success, but it dramatically improves your odds by ensuring you're always building something that brings value.

If your startup or growing business needs a product development team that knows how to bring lean principles to life, we'd love to help. Contact us to turn uncertainty into confidence and ideas into measurable results.

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