KOSH

Save Smarter. Together.

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Inspiration

We've all been there: trying to coordinate a group saving goal, like for a vacation, a shared apartment deposit, or a team project. It almost always ends in a messy spreadsheet, a chaotic group chat, and awkward reminders about who hasn't paid. This process is broken, relying entirely on social pressure.

We were inspired by this real-world problem. We also looked at traditional informal savings circles (like a susu or chit fund), which are used by millions but lack a digital, secure, and automated platform.

We asked: What if we could build a tool that keeps the "together" part of group savings but replaces the chaos with discipline? That's why we built KOSH.

What it does

KOSH is a FinTech web application that digitizes and automates savings for both individuals and groups. It's not just a tracking app; it's a discipline app.

  • Individual & Group Savings: Users can create personal savings goals or create/join public (auto-join) and private (admin-approval) groups for shared goals.

  • Personal Wallet: Every user has a secure wallet to manage funds and track their transaction history.

  • Automated Discipline: This is our core feature. KOSH tracks manual monthly contributions and automatically applies a late-payment penalty (up to 40%) to any member who misses a deadline. This removes the social awkwardness and enforces real accountability.

  • Admin-Triggered Payouts: Once a campaign ends, the group admin can trigger the payout with a single click. KOSH then automatically and fairly distributes the entire saved pot (including penalties) equally among all members.

  • Dashboard: A central hub to track all your active campaigns, group memberships, and wallet activity.

How we built it

We built KOSH as a modern, full-stack application using a MERN-stack approach, supercharged by Next.js.

  • Frontend: Next.js 15 and React 19, styled with TailwindCSS and the beautiful ShadCN UI component library.

  • Backend: We used Next.js API Routes to create a robust, Node.js-based RESTful API, handling all our business logic.

  • Database: MongoDB Atlas, connected with Mongoose, to store all user, group, and campaign data.

  • Authentication: We implemented secure, JWT-based authentication using NextAuth.

  • Deployment: The entire application is hosted on Vercel.

Challenges we ran into

The most significant challenge was designing the financial logic. We weren't just moving numbers; we were building a system of rules.

  • Safe Payout Logic: We had to build a "failsafe" system. For example, a group admin must distribute a campaign's funds before they are allowed to delete the group or start a new campaign. This prevents users' funds from ever getting "stuck" or "lost" in the system.

  • Penalty & Payout Calculations: Ensuring the penalty logic was fair and that the final payout calculation—which includes all contributions and penalties—was mathematically sound and distributed correctly was a complex task.

  • State Management: Juggling the various states of a campaign (e.g., pending, active, completed) and ensuring the UI and backend were always in sync was a fun challenge.

Accomplishments that we're proud of

  • The Automated Penalty System: This is our star. It's the core feature that makes KOSH a "discipline app" and not just another tracker. Getting this logic right was a huge win.

  • The "Failsafe" Admin Controls: We're proud of the robust, "real-world" logic we implemented for group admins. It shows we were thinking about user safety and trust, which is #1 in FinTech.

  • A Complete, Deployed Product: We're incredibly proud of building and deploying a full-stack application that solves a complex problem from start to finish.

  • A Clean, Trustworthy UI: Using Tailwind and ShadCN, we built an interface that looks professional, modern, and trustworthy—which is exactly what a user wants from a financial app.

What we learned

  • FinTech is All About Rules: We learned that building a financial app is 10% UI and 90% rules, logic, and state management. Every small feature has a cascade of "what if" scenarios you must account for.

  • Full-Stack Next.js is Powerful: We gained a much deeper appreciation for the Next.js App Router as a true full-stack framework. Handling our API, auth, and frontend in one cohesive codebase was a fantastic experience.

  • System Design > Features: The importance of planning our "safe" systems (like the payout logic) before writing any code was the biggest lesson.

What's next for KOSH

KOSH is a prototype with a powerful foundation. The next steps are all about automation and access.

  • Payment Integration: Integrate with Plaid and Stripe to enable fully automated contributions from users' bank accounts, removing the "manual" step.

  • Mobile App: Build a cross-platform mobile app (likely with React Native) to make saving even more accessible.

  • Smarter Savings: Implement AI-powered features, like suggesting savings goals based on user spending or providing smart budget recommendations.

  • Notifications: Add email and push notifications for contribution reminders, penalties, and payouts to keep users engaged.

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