SoloAgentFlow

In short6 min read

Two full-time developers spent a year building a water tracker app on nights and weekends, reaching $391 MRR and 254 active subscriptions with no paid ads. Here's what they built, what they tried, and how to apply it to your own app.

In this article

1. A Real Year-One Number, Not a Screenshot Fantasy
2. The Setup: Two Devs, Full-Time Jobs, Late Nights
3. The Numbers at a Glance
4. The Hard Part Isn’t Building. It’s Being Found.
5. Why This Model Still Works (With Caveats)
6. Realistic Adjustments If You’re Replicating This Today
7. How to Do It: Your Step-by-Step Checklist

A Real Year-One Number, Not a Screenshot Fantasy

Your feed is probably full of “$200k/month app built in 2 days” posts. A Reddit post in r/SideProject offers something rarer: an honest, unglamorous year-one report from two developers who built a subscription app on nights and weekends. By the end of this article, you’ll know exactly what they built, where their revenue comes from, which growth tactics moved the needle (and which didn’t), and a step-by-step checklist to start your own version.

The app is Waltermelon, a water tracker. After one year on the App Store and Google Play, the founders report $391 in MRR, 254 active subscriptions, and about 17K total users. That’s not life-changing money, and they don’t pretend it is. But it’s real, recurring, and built without paid acquisition, which makes it a far more useful blueprint than most viral threads.

The Setup: Two Devs, Full-Time Jobs, Late Nights

According to the founders, both of them hold full-time developer jobs. They work on Waltermelon in the evenings, usually until midnight. They’re quick to point out they aren’t “vibe coders”: they’ve been building apps for clients for 12 years.

That context matters. This isn’t a story of a beginner prompting an app into existence. It’s a story of experienced builders using AI to cover the parts of a business that two people otherwise couldn’t handle alone.

Where AI fits in their workflow

The founders say they use AI “a lot” because it’s just the two of them doing everything. Their stack and responsibilities include:

• Flutter for the cross-platform app
• Backend development
• Design, including the app UI
• Mascot animations
• Store pages (listings, screenshots, copy)
• TikToks for organic marketing

The takeaway for a solo builder: AI isn’t replacing their engineering skill. It’s acting as a force multiplier across design, content, and marketing, the areas where small teams typically stall.

The Numbers at a Glance

Here’s everything the founders shared publicly, in one place:

Metric	Reported figure
Time on stores	1 year
Monthly recurring revenue	$391
Active subscriptions	254
Total users so far	About 17K
Android users	Roughly 11K
iOS users	Roughly 5.5K
Google Play rating	4.7
App Store rating	4.8
Paid ads	A few hundred dollars of early tests that didn’t pay off
Team	2 developers, part-time

What these numbers actually tell you

Three things stand out. First, the revenue model is subscriptions, which means each new subscriber stacks on top of the last instead of being a one-off sale. Second, the ratings are strong on both platforms, suggesting the product itself isn’t the bottleneck. Third, Android drives most of the user base in their case, so don’t assume iOS-first is automatically right for every niche.

The gap between 17K users and 254 active subscriptions is the honest reality of freemium apps: most people use the free version. Growing revenue means either getting far more people in the door or improving how many convert, ideally both.

The Hard Part Isn’t Building. It’s Being Found.

This is the single most important lesson in the post. The founders say they spend most evenings looking at data, changing something, and testing it, and that “the hardest part isn’t building, it’s getting people to find the app at all.”

If you’re a developer, this should reframe your plan. With AI tools, shipping a polished app is more achievable than ever. Distribution is where side projects quietly die.

What they tried, and how it went

The founders were candid about their year of growth experiments:

• App Store Optimization (ASO): Putting “Water Tracker” first in the store title helped “a bit.” Their emphasis, not ours: a bit. Keyword-first titles are worth doing, but don’t expect a single change to transform downloads.
• Outreach to “best water tracker apps” lists and blogs: Most never replied. The founders also expressed frustration with which apps tend to appear on those lists.
• Apple featuring: They applied many times and never got picked. Featuring is a lottery ticket, not a strategy.
• Paid ads: A few hundred dollars of early test ads didn’t pay off, so everything since has been organic.
• Short-form video: They create TikToks themselves, with AI help, as part of their organic marketing.

Note: the original post is longer than the excerpt we reviewed, so this isn’t necessarily the full list of what they tested.

Why This Model Still Works (With Caveats)

A water tracker is a crowded category. So why is this worth studying?

Recurring revenue compounds. Every month you retain subscribers and add new ones, MRR climbs without you selling the same customer twice.

Low ongoing cost. The founders built it without a paid acquisition budget. If your costs stay small, even modest MRR can be profitable.

Skills transfer. Their experience applies to any simple utility app: habit trackers, budgeting tools, timers, niche calculators.

The realistic caveats

• Speed: A year of evening work produced $391 MRR. If you need meaningful income in 90 days, this isn’t that path.
• Experience gap: The founders have 12 years of client app development behind them. If you’re newer, budget more time for learning, and lean on AI carefully for code you can actually maintain.
• Crowded niches: Being good isn’t enough to get noticed in a category full of established competitors. Plan distribution before you write code.
• Your results will differ. Outcomes depend heavily on your niche, execution, and consistency.

Realistic Adjustments If You’re Replicating This Today

If you want to follow a similar path, here’s how to learn from their year rather than repeat it:

1. Pick a niche with a built-in audience you can reach. Instead of a generic utility, consider one tied to a community you’re already part of (a sport, a profession, a hobby).
2. Treat distribution as half the product. The founders found discovery to be the hardest part. Allocate as much time to marketing experiments as to features.
3. Do ASO on day one. Put your primary keyword early in your store title. It’s a small win, but it’s free.
4. Don’t bank on featuring or listicles. Apply if you like, but build a plan that works if both say no.
5. Use AI for the non-coding grind. Store copy, screenshot concepts, short-form video scripts, and design iterations are where AI saves a two-person team the most time.
6. Test ads only with a clear hypothesis and a small cap. The founders’ early tests didn’t pay off. Know what a subscriber is worth to you before spending.

How to Do It: Your Step-by-Step Checklist

Use this checklist to start a subscription utility app as a side project:

1. Choose one narrow problem. Write a single sentence: “This app helps [specific person] do [specific habit or task].”
2. Research the store keywords. Search your app category on both stores and note which words appear in top competitors’ titles.
3. Pick your stack. A cross-platform framework like Flutter, as the founders used, lets a small team ship to Android and iOS from one codebase.
4. Define free vs. paid. Decide which features stay free to attract users and which justify a subscription.
5. Build an MVP with AI as your assistant. Use it for boilerplate, UI drafts, and design ideas, but review and understand every piece of code you ship.
6. Create a character or visual hook. Waltermelon uses mascot animations. A memorable visual identity helps both store pages and social content.
7. Write a keyword-first store title. Lead with the term people actually search for.
8. Launch on both stores. Don’t assume where your users are. In the founders’ case, Android brought in the majority.
9. Ask happy users for ratings. Strong ratings like their 4.7 and 4.8 build trust for new visitors.
10. Start an organic content habit. Post short-form videos showing the app solving the problem. Use AI to draft scripts and ideas.
11. Set a weekly test loop. Each week, change one thing (title, screenshot, paywall copy), measure it, and keep or revert.
12. Track MRR and active subscriptions monthly. These two numbers tell you whether the project is compounding or stalling.

Source: One year of our side project: two devs, no ads

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