Antoine van der Lee is the developer behind SwiftLee, a wildly popular iOS development blog, and RocketSim, a developer tool that supercharges the Xcode simulator. In a conversation with Charlie Chapman on the Launched podcast, he explains how RocketSim grew from a personal side project into a business approaching $100K ARR, entirely without traditional marketing. It’s a masterclass in building for your own needs, listening to your users, and understanding that the most powerful thing a developer tool can sell is time.
The pitch that writes itself
When it comes to selling developer tools, the value proposition can sometimes get muddy. Are you selling a better UI? A new workflow? For Antoine, the pitch for RocketSim is much simpler, and it comes directly from his head of sales.
“He just tells me it’s so easy to sell RocketSim,” Antoine says. “And the reason is RocketSim is focused on reducing time spent, and it creates more time to work on actual features. There are so many solved problems in the world, but if you manage to solve the one limitation factor, which is time, and give more time to people, they will pay you.”
It’s a framing that cuts through the noise. When you pitch a “network monitor” or a “recording tool,” you’re asking developers to change their habits. When you pitch “five minutes saved every day,” multiplied across a team of engineers over a year, the ROI becomes undeniable. You aren’t selling a feature; you’re selling the ability for developers to get back to the work they actually enjoy.
The 2-year open GitHub issue
In an era of AI agents and instant answers, it’s easy to feel like every technical problem should be solvable in an afternoon. But Antoine’s journey with RocketSim proves that some problems just require you to grow into the solution.
For two years, he had an open GitHub issue for a feature that would allow developers to slow down the network specifically for the simulator, without affecting the rest of the Mac’s connection. “Every single answer you would basically find on Stack Overflow,” he recalls. “But I created that issue like, ‘Okay, I want to create a solution that works just for the simulator.’ And that issue has been open for two years. I just couldn’t find the answer.”
Instead of forcing a bad solution, he let it sit. He went to conferences, talked to other developers, and waited for new APIs. When he finally cracked it, the payoff was immense. “The moment that it worked was so amazing because I was literally thinking about it for two years,” he says. It’s a reminder that persistence is often just as important as raw technical skill.
How 40 trials became 120
When deciding what to build next, it’s easy to get distracted by shiny new APIs or personal pet features. Antoine took a different approach: he maintained a public roadmap and let his users vote.
The top-voted feature was a network monitor. When he finally released it, the impact was immediate and measurable. “I saw the active trials going from 40 a day to 120 a day,” he notes.
The lesson is straightforward but often ignored: building exactly what your users are asking for doesn’t just satisfy your current audience—it acts as a powerful re-engagement tool for developers who churned because the app lacked a specific capability. “That really just proves if you build what your users want, the real fields will follow,” he explains.
The focus trap of going full-time
The dream of going “full-time indie” is having five uninterrupted days a week to work on your app. But when Antoine finally made the leap—having already matched his salary and built RocketSim to nearly $100K in recurring revenue—he discovered a counterintuitive truth: more time doesn’t automatically mean more output.
“When I was full-time indie, I let loose of all the things that I learned as a side hustle,” he admits. “So I didn’t prioritize anymore. I didn’t plan anymore. I just started the day and I was like, ‘Okay, let’s see what I’m going to do today.’”
When you’re building a side project on nights and weekends, the extreme scarcity of time forces you to be ruthless about prioritization. When those constraints vanish, it’s easy to fall into the trap of doing everything at once and finishing nothing. To succeed as a full-time indie, Antoine had to consciously rebuild the strict habits and boundaries that made him effective when he only had a few hours a week to spare.
In the full episode, Antoine also discusses the irony of AI agents killing the blogs they were trained on, why he actively cross-promotes with competing newsletters, and the time he tried to become a world champion in darts.