Instructor JP Pro

3 apps in one. No AI content. Made by the professional himself who learned backend development to build the app. Workout, Diet and Heart Rate. Cross platform. 20+ years of data behind it.

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What was necessary to build it

  • Learned backend development via Harvard CS50x
  • Gained and loss 40lbs of fat twice to demostrate the app's formulas
  • Compiled 15+ of hand-written unique data to create the unique databases (900+ unique foods and 500+ unique exercises) which are served along side 7100+ USDA foods
  • Filmed 150+ multi-angle slowmotion videos
  • Coded the backend by hand for 2 years (4 to 14 hours of coding a day)
  • Used Claude (chat, not Claude code) to build the mobile frontend
  • Compiled scientific data for 6 years to build the app formulas
  • Kept my day job to pay the bills but reduced to a third the quantity of clients
  • Ongoing app growth, the databases come live from the app's servers to which new videos, foods, exercises, programs and more being continuously added

Inspiration

I've been a personal trainer for over 20 years. NSCA-CPT, a degree in Physical Education, Harvard Executive Education coursework in nutrition — but none of that is the point. The point is that in two decades of coaching more than 5,000 people, I watched the same thing happen so many times: someone would show up with real desire and real discipline, give everything they had for months, and still not get the results they were chasing.

In those cases where the discipline exists but not the tools is where I aim to give people what they need and where the app serves it's most important purpose.

If I can be open and clear, I never wanted settled and be known just as a Certified Personal Trainer, I always wanted to test myself to achieve more, what better way to expand my business, to challenge myself to actually reach the world but by learning to code to build my own apps... So yeah this years of coding have been extremely hard from time to time but I sure love it.

What it does

The app does three main things: Provide the person with guidance, inspiration and rules.

The app provides professional human-made exercise and explanation videos, workout and diet programs along side heart rate tracking in one single place.

Allows each user to have everything they need to achieve their goals from day one, no more excuses.

On top of the all-in-one idea the app is deeply personal and linked to me, I am the one in the 150+ slow-motion multi-angle exercise videos, within the app there are explanation videos, the workout programs, the diets and the software is built directly by myself, therefore there an intrinsic connection between the user and the human behind the app, which I think makes for a compelling experience compared to the usual corporate faceless alternatives.

How I built it

3 servers running on Azure, all working at the same time and performing different primary tasks but serving as backup for any other that fails, all that backend and database code is made by myself, the mobile apps are architected by me but I made the code using Claude, this mobiles apps do not perform logic or contain complex logic beyond the Bluetooth connection since all data comes from my servers.

What I learned

The first courses I took were from codecademy on html, CSS and JavaScript, all of those between August and October 2024 then I registered for Harvard's CS50x on October 25, 2024 and finished it on December 31, 2024, deliberately doing the entire C portion without watching a single help video — I wanted to learn the hard way (1400+ mistakes, which can be viewed on my jpca01 github account commits), thanks to that the Python portion was easy, and then came the final project which was the actual App Instructor JP webapp which is now one the brains behind the mobile apps. Everything that is live in the app comes from the backend first build for the Harvard project and other servers I have build since then. At first I faced continuous real world problems which occurred before any mobile app was published, that allowed me to greatly improve my systems before thinking about starting to build the mobile app, and so for when the time came to actually build the mobile part the backend was solid (besides serving as the mobile apps brains my backends also are currently being used daily and have been doing so for over a year by Google, Amazon, Meta, OpenAI and more, about 3 to 10k times per day, all thanks to the structure and stability of the databases and 50ms response times of the servers, eg. For example since the last model relased by OpenAI ChatGPT sends tens of users daily to my app's website for the app's exercise video guides). All the user's auth, connections, storage, live within the backend servers for I made the code myself, the frontend side was built using Claude, and it pulls everything from the servers and is build with dart/flutter which allowed for dual shipping for IOS and Android. At the same time I took great care on my work, so no logic or mathematics are performed within the mobile side, everything comes via https or pubsub wss allowing secure connections, also the mobile part incorporated the Bluetooth connection so the user can take advantage of Heart Rate monitors.

Challenges I ran into

Since I learned to code to build the app the I can say that the CS50 was the greatest challenge, learning C first was no joke, but I made it, the same way the times the server went down for obvious mistakes that skipped my eye, the translation of the databases from excel to csv to sqlite, the polar API integration, the WhatsApp API, everything was a challenge at first, but I think that is what I really value, the satisfaction of actually make it work.

Accomplishments that I'm proud of

The first that comes to mind is the backend, I have 3 servers under the hood of the mobile apps, they perform different main task but they also serve as a backup for the other in the case on any problem, this server interconnection makes the app reliable always and gives me a lot of peace of mind. Also since the servers have been running for almost 2 years now and are used thousands of times daily by all the major companies of the world daily without problems makes me incredibly proud.

What I learned

Well, I learned to code haha, the backend is solid and since I started only a couple of years ago there is one thing I really learned, the respect and compassion for my fellow coders, I have the advantage of working solo (yeah when it comes to take decissions fast is a real advantage), but within my personal trainer business I have had many software engineers as personal clients and I have always seen their struggle, I now know a bit more from being within the trenches and not just from the outside how hard is to keep up without sleep, but I also know that it is possible, and I really really like it haha.

What's next for Instructor JP Pro

Within a few hours of the launch on Android the app got hundreds of downloads with the the prepared advertising strategy, but that doesn't mean it will continue to so, therefore now comes the part where the actual results show, marketing continuous improvement, user retention and actual revenue-cat- haha. Since 2012 and to this day I handled the campaigns of Facebook, Instagram and Google for my own bussiness and other endeavours, so I know how hard is it and the investment of time and money required, therefore I cannot depend on just money or great SEO, since 2021 I have been competing in Body Building and performed some stunts by gaining and losing 20kg of fat in order to demonstrate how reliable and impressive can the mathematics and results achievable via the algorithms within the app's systems be. So the next steps are not only to keep improving the code but to show people what is actually possible via the app's formulas and their own personal resolve.

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