Cosmin Rusu

Transforming Visions into AI MVPs & Products | Founder @Duty Ventures | Ex {Google, Apple and Amazon}

Hi, I’m Cosmin, the Founder and Lead Engineer of Duty Ventures. 

After some experience as a software developer in companies such as Google, Apple, and Amazon, I decided to launch my project.

With several former colleagues and college friends, we launched our own startup specializing in software development for entrepreneurs and customers needing software development services. 

Duty Ventures is all about developing software products from start to finish, thanks to the experiences we have all acquired in the past years.

One of our most successful services is aimed at entrepreneurs and early-stage founders, for whom we provide an MVP-builder service getting their product from 0 to 1 within weeks!

However, our services are not limited to that. The teams we create do much more than just create MVPs and are able to adapt to the different technologies requested, all of this in an agile way.

Our most recurrent services are the following:
- MVP creation
- Custom Software Development
- Blockchain Development
- Mobile Development
- Checkout pages
- E-Commerce

And our most used technologies are:
- Ruby on Rails
- React
- React Native
- Java
- NodeJS


If you want to learn more about how we can help you, head over to: https://dutyventures.com


Phone: (+1) 669 200 9568 / (+40) 754 973 314
Email: cosmin@dutyventures.com

Founder & Lead software engineer

I'm leading a software development agency focused on fast iterations. Most of our clients are shipping more features, responding faster to support tickets, and have accelerated growth because of us.

We focused on HealthCare a lot lately due to the accelerated digitalization in this industry. I am a strong believer that we can make healthcare more technically advanced via pure software. 

In terms of technologies, our previous projects involved Ruby on Rails, React, React Native, Scala, Java, Kubernetes, GCP, AWS (ECS, RDS, AKS), Stripe Connect, HIPAA compliance.

Some of our previous clients: 
- Spotify
- Colgate
- Go4Ellis (incl. HIPAA compliance)
- KindBody (+1 HIPAA)
- NXT Sports
- Noom (Healthcare)
- Mochila Fulfillment
- 3Step
- Mylk Guys (YCombinator)
- NLV Productions
- SH Technologies
- One Step Software (Techstars)
- Ergodic Labs
- Med Prep
- Testing Psych
- Abundance Digital
- Tookitaki

I upgraded to a Standing Desk half a year ago! Worth it? Not really - I find I very rarely use it, and recently just thought about it... We tend to stick to what we're comfortable with, to what we are used to. It's hard to get into a new habit. But once it becomes a habit, it's almost like second nature. In 2026, I plan to use it more often.

Product-minded Devs | Founder @Duty Ventures | Ex {Google, Apple and Amazon}

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Are you behind on your Stripe API upgrades? Be careful! Stripe is sunsetting some very important and widely used features.

Stripe::Charges, Stripe::Sources are being deprecated and replaced with the more modern equivalent, the Stripe::PaymentIntents and Stripe::PaymentMethods. While you can still use them, you should plan to upgrade your integrations to avoid imposed deadlines during your busiest season...

In fact, one of my long-term clients started contracting us for a challenging Stripe Connect upgrade, back in the days when Stripe rolled out mandatory Know-Your-Customer (KYC) flows. 

To learn more, keep an eye on the Stripe Change Log: https://lnkd.in/dBm7PKvf

In B2B sales, I learned a valuable lesson: it's easy to focus on getting new customers, but super hard to get them to sign up. However, it's hard to focus on existing (or past) customers, but super easy to get them to sign.

How do we work remotely as a team? What tools to do we use? Let me break it down to you.

- Communication: Slack
- Email: GSuite
- Meetings: Google Meet
- Project Management: Trello - very simple and clean. For more complex projects - JIRA
- Code Editor: Windsurf

That's it - nothing fancy, nothing complex. This is our "productivity" stack. Next, it's up to the individual to figure out what works for them. We don't want to force anyone into using anything that they aren't excited about.

Learning from others' mistakes! Here's another example of failures in marketing that will lead to bad outcomes.

I got a cold email from a company selling cybersecurity services. I clicked on their website, and I got this pop-up.

I get that sometimes marketing emails don't go through strong security checks, but you can imagine how a lead would react if you send such emails.

Are you rich when you make 25x your annual spending? Is that the "golden ratio" of financial independence?

Here's a great hack I naturally learned that improved my sales skills:

Whenever you get a cold email, cold LinkedIn message, or even a cold call, answer and be receptive - be the buyer!

I'm almost always doing this, just to see how the best salespeople perform. If I forget about them, do they follow up? How many times? If I simply forgot to sign the papers, how do they gently ask me to sign?

I'll give you an example: I get called a few times per quarter from mobile carriers that are trying to sell me their phone services, like SMS, voice, and internet. I almost immediately say:

- I'm not interested - I already have an unlimited cheap subscription, thanks! 

However, last time I got a call, I asked them to tell me more, and asked:

- How are you better than this other subscrption I have?

Next time I send a message regarding custom software development work, I'll understand that most people like where they are at and don't want to change their teams. However, if you approach the conversation from their angle, you'll find that if you can tell them something that they don't know already, you might at least have a small conversation.

Doing this will make you more empathetic to your next clients, and you'll learn faster what works, and what doesn't work in sales.

Not to mention you'll see how easy it is to "slip" through the funnel 😆!

Careful - we re getting replaces with cached code written by AI - so all our code will have the same bugs and issues that we will have to fix… that would be a cool service businss idea: bug fixes for your AI agentic coder

Cute how devs think they’re gaming the system with $200/month for unlimited Claude Code. ”Oh, I’m burning $2K in tokens with 6 Claude Codes before breakfast!”

Buddy, you’re not burning tokens. You’re burning markup.

I wired Claude Code into a dedicated vLLM to see what’s really under the hood. Six hours of pure coding and debugging later:

- 47M prompt tokens
- 45M prefix-cache hits
- 96.39% cache hit rate (token-weighted)
- Actual compute: 1.3M prefill + 300K generation tokens

That’s not GPUs working hard. That’s a cache with delusions of grandeur.

Anthropic’s “subsidized” coding plan isn’t subsidized; it’s a cache lottery. When they serve you a well-quantized Haiku/Opus hybrid that’s 96% memorized boilerplate, the marginal cost rounds to zero. The limits are fake scarcity. The $100 and $200 tiers are merely psychological anchors.

You’re not paying for compute. You’re paying for the feeling of unlimited power while they throttle you at 5 hours/week limits to protect GPU margins.

Agentic coding is a brilliant pricing hack. Just don’t confuse it with actual token economics 🤡

Make sure you own your AI. AI in the cloud is not aligned with you; it’s aligned with the company that owns it.

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