Crypto Properties

Buying property abroad used to take six weeks of paperwork. Built a blockchain property platform. The whole purchase is one transaction, with proof of ownership stored on-chain forever.

• 01User surface

  The whole experience the user sees

  This frame shows the live product: property marketplace on ethereum · every sale carries an nft ownership certificate. Every component is ours · scope, design, code, deploy.

• 02Stack behind the screen

  What's powering it: Express, Hardhat, Mocha

  5 stack components run behind this frame · Express, Hardhat, Mocha drive the visible UI; the rest sit in the data layer. All studio-owned.

• 03What we shipped

  Property catalogue with pricing

  Instant ownership transfer on-chain

• 04Status

  Private deploy · under NDA.

  Per the client's request the URL stays private · the build, architecture, and lessons can be shared in a scoping call.

• 01 · BRIEF

  Title transfer is the bottleneck.

  Cross-border title verification takes weeks of paper. Spec'd an atomic-swap pattern: payment + ERC-721 certificate transfer happen in a single Ethereum tx.

• 02 · ARCHITECTURE

  Stack decisions before any code.

  Decision doc captured the data flow, Express, Hardhat, Mocha, Vite role split, and the failure modes we'd handle in v1 vs defer. Cross-service boundaries (where AI ends and the web app begins) were drawn here so neither side leaked into the other later.

• 02 · BUILD

  Hardhat contracts + Vite client + indexer.

  Listing contract holds escrow + ERC-721, Mocha invariant suite covers the swap path. Express indexer mirrors on-chain state for fast catalogue queries · the marketplace UI never blocks on RPC.

• 04 · POLISH

  Performance, accessibility, and observability.

  PSI / a11y / coverage budgets enforced as launch gates. Logging + metrics wired before cut-over · the team can answer 'is it working?' from a dashboard, not a Slack thread. Threat-model checklist signed off before traffic hits the box.

• 03 · SHIP

  Live on testnet · audit-ready paperwork.

  Foundry-style coverage > 95%, threat model document, slither + mythril clean. Audit dossier handed back · production deploy is a customer call.

• 01Contracts

  Atomic listing + transfer

  Single tx settles payment, escrow release, and ERC-721 transfer · partial-failure paths covered by tests.

• 02Indexer

  Express mirror of on-chain state

  Off-chain catalogue queries hit the indexer, not the RPC · marketplace UI feels SaaS-fast despite running on-chain.

• 03Provenance

  On-chain ownership history

  Every transfer is a public record · forging a paper trail isn't possible.

• 04Tests

  Mocha invariant suite + > 95% coverage

  Suite covers the happy path, the partial-failure paths, and the adversarial paths · audit prep was light.

• 
  01Frame

  Marketplace · ETH-priced listings, hashed owner per card

  Six properties across HU / CH / HR / DE / IT / ES priced 0.85-5.4 ETH · each card carries the owner address (`0xf39F...2266`), location pin, listing # and a 'Buy now' button. The catalog reads like a normal marketplace; the chain is invisible plumbing.

• 
  02Frame

  Hero + listing form · the seller side

  Hero declares the value prop in plain English: 'Tokenize, list and trade real estate as NFTs.' Below it, the 'List a new property' form (ERC-721 · on-chain) asks for title, location, price and images · the same chain that runs the marketplace.

• 
  03Frame

  Listing form filled · Parkside Townhouse, Vienna

  Operator types the title and location, the form auto-saves to the local draft and shows the ERC-721 contract type chip top-right · the seller knows exactly what's being minted before they hit submit.

• 
  04Frame

  Image upload · 5 photos bound to the listing

  Native macOS picker selects 5 property photos (01-exterior, 02-livingroom, 03-kitchen, 04-bedroom, 05-garden) at 1600×1067 each · they're stored alongside the on-chain metadata so the listing carries a real visual story, not a single thumbnail.