I Built a Risk-Driven Stock Portfolio Optimizer (And What I Learned)

Dany Trakhtenberg — Thu, 25 Dec 2025 01:07:44 +0000

Like many developers, I’ve seen a lot of “portfolio builder” tools that promise outperformance with vague AI claims or black-box optimization.

I wanted to explore a different angle:

What if risk controlled portfolio structure — not just which stocks are labeled “risky”?

So I built StockRisker, a risk-driven stock portfolio optimizer that focuses on constraints, explainability, and realistic tradeoffs rather than guarantees.

👉 Live demo: https://stockrisker.com/build

The Core Idea

Most retail investing tools treat risk as a side effect:

Higher risk → “riskier stocks”
Lower risk → “safer stocks”

In practice, that’s not how portfolios behave.

Risk tolerance usually affects:

How concentrated you’re willing to be
How much sector exposure you allow
How asymmetric your allocations can get

So in StockRisker:

Risk directly controls portfolio constraints
Higher risk = fewer penalties, higher concentration caps
Lower risk = stricter diversification rules

Risk isn’t just a label — it’s a structural input.

How the Optimizer Works (High Level)

The optimizer is built around three layers:

Risk Mapping

A user selects a risk level (1–10).
That value dynamically controls:

Max allocation per stock
Max allocation per sector
Strength of diversification penalties

At high risk levels, penalties are relaxed instead of forcing “safe” portfolios that don’t match user intent.

Constraint-Driven Portfolio Generation

Portfolios are evaluated under:

Hard constraints (must never be violated)
Soft constraints (applied as scoring penalties)

This avoids a common failure mode where optimization technically succeeds but produces unrealistic portfolios.

Explainable Scoring

Each portfolio is scored using a weighted function that balances:

Expected return estimates
Volatility and diversification
Concentration and sector exposure

If results look suspicious (e.g., very high return vs relatively low volatility), the UI surfaces contextual warnings instead of hiding the risk.

No “guaranteed outperformance” messaging.

What I Optimized Against

One of the most interesting challenges wasn’t math — it was expectation management.

Some things I intentionally avoided:

No promise to beat the S&P 500
No opaque AI model
No single “correct” portfolio

Instead, the tool helps users reason about tradeoffs:

Concentration vs diversification
Risk appetite vs volatility
Simplicity vs optimization

Tech Stack

Backend: TypeScript + Node.js
Modular optimizer design (risk mapping → constraints → scoring)
Cached stock universes for performance and stability
Frontend: Clean, minimal UI focused on clarity and explainability

The architecture is designed to support future extensions like:

Backtesting
Risk-adjusted metrics (Sharpe, drawdown)
Scenario simulations

What I Learned

Risk is a UX problem, not just a math problem
Users need to understand why a portfolio looks the way it does.

Constraints matter more than algorithms
A simple optimizer with good constraints beats a complex one without them.

Transparency builds trust faster than performance claims
Surfacing limitations actually increases confidence.

Introducing the Schengen Area Calculator: Plan Your European Travels Seamlessly

Dany Trakhtenberg — Sun, 23 Jun 2024 20:19:22 +0000

Are you planning a trip to Europe and worried about the 90/180-day Schengen visa rule? Meet the Schengen Area Calculator – your ultimate tool for tracking stays and ensuring compliance with the Schengen visa regulations.

What is the Schengen Area Calculator?
The Schengen Area Calculator is a web-based tool designed to help travelers like tourists or digital nomads to track their stays within the Schengen Area. This tool ensures that you comply with the 90/180-day rule, preventing overstaying, fines, or even bans from the Schengen countries.

Key Features
Stay Tracking: Log your entry and exit dates for every trip to the Schengen Area. The calculator keeps track of your stays and alerts you if you are close to violating the 90/180-day rule.
Violation Alerts: Receive instant notifications if your planned stays exceed the allowed duration, helping you avoid potential issues with visa regulations.
Visual Timeline: Our interactive Schengen Chart offers a visual representation of your stays, giving you a clear overview of your travel history and future plans.
Country Information: Access detailed information about each Schengen country, including visa requirements and exemptions.

How It Works
Input Your Stays: Enter the dates of your stays within the Schengen Area, including the start and end dates of each stay and the country visited.
Track Your Stays: The calculator will automatically track your stays and calculate the total duration of your stays within the last 180 days.
Receive Alerts: If you are close to or have exceeded the allowed 90 days, the tool will alert you, ensuring you can take action to avoid any issues.

New Feature: Days Left Calculator
We recently added a feature to calculate the last day you can stay in the Schengen Area if you want to maximize your 90 days. This feature helps you plan your trip efficiently by showing the remaining days starting from a specific stay and the next possible entry date after the 180-day period.

Why Use the Schengen Area Calculator?
Avoid Overstaying: Stay within the legal limits and avoid fines or bans.
Plan Efficiently: Use the tool to plan your trips and make the most of your stay in Europe.
Peace of Mind: Travel with confidence, knowing that you are complying with visa regulations.
https://schengen90.com
Planning a trip to Europe? Check out the Schengen Area Calculator and start tracking your stays today!

Technical Implementation

Frontend
The frontend is built using React and Next.js, which allows for server-side rendering and static site generation, improving SEO and performance.
React: Used for building the user interface, ensuring a responsive and interactive experience.
Next.js: Utilized for its server-side rendering capabilities, which enhance SEO and load times.
React Bootstrap: For styling and responsive design, making the tool accessible on both desktop and mobile devices.
Firebase Authentication: Implemented for user login and data persistence, allowing users to save their travel data securely.

Backend
The backend leverages Firebase for both hosting and database services.
Firebase Firestore: Stores user data, including travel dates and country information, ensuring secure and scalable data management.
Moment.js: For date manipulation and formatting, making it easy to calculate durations and validate dates.
react-dates: Provides a robust date picker component, ensuring users can easily select their travel dates.
react-helmet: Manages meta tags for SEO, improving the visibility of the tool on search engines.

Feedback and Support
We'd love to hear your feedback! If you have any questions or suggestions, please feel free to reach out.

Forem: Dany Trakhtenberg

I Built a Risk-Driven Stock Portfolio Optimizer (And What I Learned)

Introducing the Schengen Area Calculator: Plan Your European Travels Seamlessly