Przemysław Zalewski

Looking for a technical co‑founder?

A business partner for your SaaS or app

You built the product after hours, maybe with Claude or Lovable. It works, and now come payments, app stores, the first paying users and the question of what next. I have shipped products since 2009 and can join as a co‑founder or on an hourly contract.

Book a free 30‑min call →

Contract: $36⁠–⁠54/h. Equity and revenue share are agreed on the call. Details in the configurator →

Przemysław Zalewski

Sound familiar?

Problems I solve as a technical partner in 2026

I built the product alone with AI. Where do I find a technical co-founder?

Carta’s Founder Ownership Report 2026, published in March 2026, shows that 36% of startups founded on Carta in 2025 had a single founder, up from 31% in 2024, yet among startups that raised venture money two-founder teams were the most common. Investors and bigger customers still ask who runs the code when it breaks.

I join as a co‑founder with vesting, for a share of revenue or on an hourly contract, picked on your numbers. I was the founding engineer of Sandtime.io, which has run in production since 2018. In March 2021 I scoped a two‑sided marketplace MVP for a client page by page, with an estimate, and proposed launching without payments so early users could fill the platform first.

Our app update won’t upload to App Store Connect

Since 28 April 2026, apps uploaded to App Store Connect must be built with Xcode 26 or later and an iOS 26 SDK. A side project on an older Expo, Capacitor or React Native setup cannot ship even a bug fix until its toolchain is upgraded.

I upgrade the toolchain and dependencies in waves you can revert, then take the build through review. I have shipped 25+ apps and build for iOS, Android, macOS and Windows end to end, store review included. Patriot Mail has been on the App Store for iOS and macOS since April 2026.

Who patches our app at night when a critical CVE drops?

React2Shell (CVE‑2025‑55182), a remote code execution flaw in React Server Components rated 10.0, was disclosed on 3 December 2025 together with fixed versions. A founder without an engineer on call finds out after the damage.

As a partner I follow the security advisories for your stack. When React2Shell was disclosed, I patched client apps the same day. On a Saturday morning in October 2026 a production host froze; I had it back within minutes, then proposed the updates and auto-restart that keep it from repeating.

Facing one of these? Book a free 30‑min call →

Scope

Three ways to work together, and what I bring

Equity

For a product with users and a plan. I become a co‑founder with vesting, so we both keep what we earn by working.

A share of revenue

No company needed yet. I take a percentage of revenue for the work I put in, written down with a cap and an exit.

A contract

The plain option: hours at the rate in the configurator, no strings. Often the right start before anyone talks about equity.

What I bring

Architecture and code, payments and subscriptions, App Store and Google Play, analytics, and honest calls on what to cut.

Process

How it works

  1. A call about the product

    What it does, who uses it, who pays, what you need. If I am not the right partner, I say so.

  2. A small piece together

    A few hours on one real problem, so we both see how the other works before signing anything.

  3. The agreement

    Equity, a share or a contract, with what each of us does, how decisions are made and how either of us can leave.

  4. A review after three months

    On the numbers: users, revenue, time spent. Then we keep going, change the deal or part as friends.

Where it fits

  • A SaaS or an app built as a side project, with the first users asking for more.
  • A product built with Claude, Lovable or Bolt that needs an engineer who has run one in production.
  • An app ready for the App Store or Google Play that nobody has published yet.

Track record

Proof

4,000+ freelancers and teams use Sandtime.io, the SaaS where I was the founding engineer. It has run in production since 2018. Before that I published 25+ apps with 3.7M+ downloads. Both stories are below.

Sandtime.io, built at Sanddev: founding engineer, eight platforms, one codebase

The problem
A time-tracking SaaS had to live where people work: desktop tray, browser, phone and app stores.
What I did
I authored the original product vision and architecture in 2018 and made the first commit. React Native wrappers for iOS and Android, Electron for macOS, Windows and Linux, a Chrome extension, multi-tenant routing, SSO, Dockerized services, Paddle and Mac App Store subscriptions, CI/CD.
Result
Eight platforms shipped and run in production. The only engineer active in every year of the product, 8,000+ commits and close to half of all merges to trunk. In 2026 alone: 270+ tagged releases in ten months, about 99% of support answered by me, and a vulnerability disclosure program with a public Hall of Fame.

8 platforms 8,000+ commits since 2018 Open ↗

See also: Mobile & desktop apps · SaaS & MVP

Offer: Your company tool, sold to other companies (SaaS)

Taking over growth: SEO, GEO and dashboards leadership reads

The problem
Organic acquisition was close to zero and nobody could say which feature moved which number.
What I did
A tracking plan per feature, PostHog KPI dashboards, SEO and GEO work on landing pages and help, with help, changelog and landing pages treated as one body of context for people and bots.
Result
Organic acquisition grew from near zero: in one 28‑day window organic clicks rose 116% and impressions 2.5×. Leadership gets its numbers from dashboards, not from asking. Numbers stay relative on purpose.

PostHog SEO + GEO

See also: PostHog & product analytics

25+ apps, 3.7M+ downloads, published worldwide

The problem
Between 2009 and 2017 the Windows Phone and Windows Store ecosystem needed apps and had few developers.
What I did
C#, XAML and ASP.NET. Localization into dozens of languages, store listings, ads and in‑app monetization, client apps for Polish media brands, plus game development on PC and Xbox 360 before that. Before Windows Phone 7 allowed background tasks, my Gadu‑Gadu client kept receiving messages by running as a background audio agent: whenever the audio stream asked for more data, it polled the chat servers and returned silence. Later a push proxy on my own server replaced the hack.
Result
25+ apps and 3.7M+ downloads. My Gadu‑Gadu client was the most downloaded app on the Polish Windows Phone Marketplace in its first week, and its successor Pogaduszki won its category at AppAward 2013 out of 300 entries. The habit of shipping, watching users and fixing what they say started here.

25+ apps 3.7M+ downloads

Sources: AppAward 2013 win (Antyweb) · wp7.com.pl, 2012 · Telix.pl, 2012 · Komórkomania, 2012 · OnMSFT, 2013

See also: C# & .NET (legacy) · Games

Want the number before the call?

Contract: $36⁠–⁠54/h. Equity and revenue share are agreed on the call.

See price and start date → Book a free 30‑min call

Good to know

Polish company law facts for founders and technical partners

A P.S.A. can issue shares for work

In a simple joint-stock company (P.S.A.) shares can be paid for with work or services. A sp. z o.o. forbids that (Commercial Companies Code).

Minimum capital: 1 PLN, 5,000 PLN or 100,000 PLN

The minimum is 1 PLN for a P.S.A., 5,000 PLN for a sp. z o.o. and 100,000 PLN for an S.A. (Commercial Companies Code).

Selling sp. z o.o. shares needs a notary

Transferring sp. z o.o. shares needs notarized signatures unless the company used the S24 template. P.S.A. shares transfer in documentary form, such as an email (Commercial Companies Code).

A P.S.A. register costs money every year

A P.S.A. shareholder register must be kept by a notary or a licensed securities firm (Commercial Companies Code).

Founder shares can protect control

A P.S.A. can issue founder shares that keep a set share of votes after every later issue (Commercial Companies Code).

FAQ

Questions

Will you work for equity?
Sometimes. Equity or a share of revenue only where there are users or paying clients and a plan to sell. Before that a contract is the honest option, and we can switch later.
I have no company. Can you sell it on yours?
Not as a start. Selling as the company of record comes with taxes, liability and data agreements, and it makes sense once revenue is real. Until then we pick a simple setup with an accountant.
What does a contract cost?
The rate in the configurator, the same as for my other work. A mix works too: a lower rate plus a share of revenue.
What if it does not work out?
The agreement says how either of us can leave from day one. Equity vests over time, so nobody keeps what they did not earn.
My project is small. Can you just help?
One small project a month, a few hours, for free or in exchange for a reference: a public review and permission to show the project as a case study.
Can a technical co‑founder get shares for work in Poland?
In a P.S.A., yes: the law lets work or services pay for shares. A sp. z o.o. forbids it, so other structures are needed there (Commercial Companies Code).
Who owns the code a partner wrote before joining?
Copyright passes only for the fields of use the contract names, in writing (Copyright Act). Put the transfer in the partner agreement, not in a handshake.
I built the product alone with AI. Where do I find a technical co‑founder?
Carta’s Founder Ownership Report 2026, published in March 2026, shows that 36% of startups founded on Carta in 2025 had a single founder, up from 31% in 2024, yet among startups that raised venture money two-founder teams were the most common. Investors and bigger customers still ask who runs the code when it breaks. I join as a co‑founder with vesting, for a share of revenue or on an hourly contract, picked on your numbers. I was the founding engineer of Sandtime.io, which has run in production since 2018. In March 2021 I scoped a two‑sided marketplace MVP for a client page by page, with an estimate, and proposed launching without payments so early users could fill the platform first.

In 30 minutes you will know if we are a fit

You bring the problem, I bring the questions. Want a number first? The configurator shows hours, a price range and the start date.

Book a free 30‑min call Email me instead

or write to ciunkos@gmail.com

After you book you get a calendar invite. Nothing else to fill in.

My pledge

  • Reply within 24 hours. I reply within 24 hours on working days, personally, not a bot. Weekend messages: by Monday noon.
  • Late means free. If I am late, the first hour of work is free. You do not have to ask.
  • Scope in writing within 24 hours. A free 30‑minute call with no company deck, then the scope and the price in writing within 24 hours. You decide.
  • The person who does the work. You talk to the person who does the work. No sales layer, no handoff.
  • Follow‑up only with news. I follow up only when I have something new for you. Never a “did you see my offer”.
  • Honest “not a fit”. If I am not the right person, I say so on the call and point you to someone who is.

Calls this week · work can start now · B2B contract · Wrocław, Poland (CET), remote

You own the code, domain and accounts from day one. Nothing is held hostage.