The problem Walt solves

Young people in Indonesia and Southeast Asia live with fragmented digital finances: one app for crypto, another for e‑wallet, another for banking, plus separate investing apps. This makes it hard to see their true net worth and forces them to jump between several apps just to complete simple tasks like topping up, sending money, or paying for a night out.

At the same time, crypto is growing as an investment asset, but is barely connected to everyday spending. To “pay with crypto”, users must sell on an exchange, wait for funds to reach their bank or e‑wallet, then pay merchants via QRIS. The process is slow, confusing, and error‑prone.

Social situations like splitting rent, restaurant bills, or tickets are still handled through screenshots, manual calculations, and long chat threads asking friends to transfer. This wastes time, creates friction, and often makes people uncomfortable chasing payments. There is no wallet that combines crypto assets, fiat (IDR), QR payments, and automatic split bills into one simple, regulation‑compliant experience.

The solution we offer
The solution is Walt, a crypto–fiat e‑wallet designed to be the everyday crypto wallet for Indonesia and Southeast Asia. Walt combines:

1. One wallet, two pockets
2. Three core journeys in one app – Grow, Send, Spend

• Grow: buy and hold crypto, optionally earn yield or set up simple auto‑invest.
• Send: transfer money to friends in crypto or IDR, with smart split‑bill built‑in.
• Spend: pay any QRIS merchant or card terminal using funds from the Spend pocket or, when needed, from converted crypto in the Invest pocket.

How It Works (High Level)

QRIS Payment Flow

1. User scans QRIS code; app parses EMVCo payload
2. Backend fetches real-time crypto/IDR rates and creates a unique orderId
3. User approves payment; smart contract locks funds in escrow
4. Backend verifies on-chain event and triggers IDR disbursement
5. Merchant receives IDR via bank transfer

Other flows (Split Bill, P2P, Swap) follow similar intent-based, on-chain enforced lifecycles.

How I built it
Walt is built using a combination of design thinking and a layered technical architecture.

1. Empathy & problem discovery
Interviews and observations with students, young professionals, early crypto adopters, and freelancers were used to map the main pain points: fragmented wallets, no clear separation between investment and spending money, messy split bills, and idle crypto stuck on exchanges.

2. Define & ideation
From these insights, the core concept “Grow, Send, Spend” and the metaphor of “one wallet with two pockets” were defined. End‑to‑end user journeys were drafted—from onboarding and top‑up, to buying crypto, sending money, and paying QRIS or group bills.

3. Design & prototyping
Wireframes and UI designs (in Figma) were created for the main dashboard, Grow/Send/Spend flows, and the split‑bill screens.

In parallel, the technical architecture was specified:

• A mobile app (Flutter) on the frontend.
• A backend (TypeScript) for APIs and business logic.
• A relational database (PostgreSQL) and irrelational database (Firebase) for off‑chain data.
• Smart contracts on a blockchain (Lisk) to implement the two‑pocket model, split‑bill escrow, and crypto balances.
• Integrations with local exchanges and payment gateways for crypto buy/sell, QRIS, and IDR settlement.

Links Smart Contracts (Verified, On-Chain):

• Split Bill Contract (waltSplitBillV5)
  Handles trustless split bills with auto-completion and pull-based refunds.
  🔗 https://sepolia-blockscout.lisk.com/address/0x998C402E2d5A55EC599C84B7B1C446732b29E5F3

• Token Swap Contract (WaltSwapV2)
  Provides atomic swaps between LSK, ETH, and POL with slippage protection and deadline validation.
  🔗 https://sepolia-blockscout.lisk.com/address/0x31169C501C316Fa6ec2e4E483ab32C09F8337149

• QRIS Payment Contract (WaltQRPayV3)
  Manages multi-token QRIS payment escrow, settlement lifecycle, and platform fee enforcement.
  🔗 https://sepolia-blockscout.lisk.com/address/0x4f11677bcF14FEEfD906Dd978a4E4Ad54b4Ce194

4. Implementation & iteration
An initial prototype was deployed in a testnet environment:

• P2P transfers, split bills, and QRIS simulation ran with test assets.
• Usability tests with a small user group validated and refined the Grow, Send, Spend flows.

Challenges we ran into

Several key challenges emerged while designing and building Walt:

1. Regulation and compliance
Combining crypto with IDR payments requires a very clear understanding of regulations: crypto is treated as an asset, while IDR is the only legal tender. The challenge is to architect transactions so that merchants always receive IDR and all crypto activity routes through compliant partners, without breaking the user experience.

2. Balancing UX simplicity and security
Users want e‑wallet‑level simplicity, but crypto introduces additional security constraints—private keys, wallet recovery, and irreversible transactions. The challenge is to deliver smooth onboarding and login (e.g., smart‑contract wallets, social login, or controlled custody) without compromising safety.

3. Complex multi‑party integrations
Walt relies on several external systems: a crypto exchange, a payment gateway for QRIS, banks/e‑money providers, and the blockchain network. Making them work together reliably—handling latency, failures, and reconciliation between on‑chain and off‑chain balances—is a significant engineering challenge.

4. User education and expectations
Many users like the idea of “spending with crypto” but underestimate volatility and the mechanics behind conversion. The challenge is to build lightweight, in‑context education (tooltips, warnings, suggested allocations) that protects users while keeping the product fast and enjoyable.

5. Designing a revenue model that feels fair
Walt monetizes through fees on P2P transfers, swaps, split bills, and QRIS payments. The challenge is to set fee levels that sustain the business yet still feel fair and transparent to users used to low‑cost fintech. This requires careful modeling, clear fee disclosure, and continuous testing against user sentiment.