BlocksMaples: a P2P crypto marketplace with USDT escrow
An API, a web app, an iOS/Android app and an admin back office for BlocksMaples, in English, Korean and Chinese.
Read the buildMobile apps with the backend behind them
We build iOS and Android apps in React Native (Expo), together with the API, admin panel and wallet flows they depend on. That includes crypto apps: wallets and P2P trading with escrow.
Talk to an engineer, not a salesperson.
5.0 out of 5 starsClient ratings
MO-01Trade · Wallet · Support
IllustrationThe problem
The hard part is behind the screen
Most problems users report in an app aren't in the screens. They're in what happens behind them: a connection that drops mid-payment, an old app version calling a changed API, a balance that's out of date.
Mobile networks fail constantly, and old app versions live in the wild for years. An app that assumes connectivity and a current API will produce support tickets that look like bugs but are architecture decisions. Offline tolerance and API versioning are choices made at the start.
What we build
What we build for mobile
The app, and the parts behind it that decide whether it works.
iOS and Android from one codebase
React Native with Expo, so both platforms ship from one codebase. When a feature needs native code, that part gets a native module.
Offline tolerance
Local state and queued actions, with a defined way to resolve conflicts when they sync late.
Wallet and payment flows
Deposits, withdrawals and balances shown honestly: pending, confirmed and failed look different. Sensitive actions sit behind a one-time code, a fingerprint or a face check.
API versioning
API contracts that evolve without breaking installs nobody upgraded.
Admin panels
The back office your team runs the product from: users, KYC review, disputes, support and reports.
Evidence
A whole product, delivered as one
BlocksMaples, a peer-to-peer crypto marketplace, named with the client's permission.
- 3 apps (API, web, iOS/Android)
- English, Korean and Chinese
- 35 mobile screens
- 38 web routes per language, 13 of them admin
- 24 data models
Ratings, reviews and engagement dates come from client contracts delivered through Upwork, checked 24 Sep 2026. '…' marks where a quote was shortened. Client names stay private.
Crypto apps
P2P crypto exchange app development
A P2P trading app is an escrow and dispute system with a mobile interface attached. We scope it that way, before designing a single screen.
- Escrow rules: when the seller's funds lock, who can release them, and what happens when one side goes quiet.
- Deposits re-verified on-chain before they're credited.
- Withdrawals behind limits, one-time codes and a signing service kept off the public API.
- KYC with manual review, merchant ads, referrals and real-time support chat.
- Admin tools for disputes, with a record of every step.
Detail
Escrow can live in a smart contract or in the platform's ledger. Each has different custody, cost and dispute trade-offs; we decide which in the architecture step.
Crypto apps
Crypto wallet app development
Wallet apps come in two shapes: the user holds the keys, or the platform does. The choice is the highest-consequence decision in the product, and each shape needs a different design.
- User holds the keys: key material stays on the device, in the phone's keychain or keystore, with a recovery path users understand.
- Platform holds the keys: per-user deposit addresses, and signing in a separate service using a cloud key-management service, never on the API server.
- Either way: transaction states that match the chain, and no balance shown as final before it is.
Languages
Multilingual apps
Localisation works best when it's designed in from the start: every string translatable, numbers and currencies formatted per locale, and layouts that survive longer languages.
BlocksMaples was built in English, Korean and Chinese, on web and mobile.
Release
Ready for app-store review
Store reviewers check more than the app. We prepare account deletion, a reviewer account, privacy details and release builds, so the review is about your product, not missing basics. We prepare for review; the stores decide approval.
Process
How a mobile project runs
Four steps. You get something you can read at the end of each.
Discover
Your users, markets and languages, what must work offline, and who holds any funds or keys.
You get
A written brief.
Architect
The API contract and its versioning, offline sync, custody, and a map of the screens.
You get
An architecture doc, the key decisions (ADRs) and a milestone plan with estimates.
Build
The app and its services together, with test builds on your own phones.
You get
Regular demos and written updates.
Validate and hand over
Testing on real devices and weak networks, then release builds prepared for store review.
You get
UAT sign-off and handover notes.
Pricing
How pricing works
A paid discovery sprint, then fixed-price milestones. Ongoing work can run on a dedicated engineer by the month.
What changes the price
The number of screens and languages, whether the app holds or moves funds, offline needs, and how much of the backend and admin panel is new.
- Discovery sprint
- Fixed-price milestones
- Dedicated engineer, monthly
- Hourly
Start here
Not ready to talk?
Scope your project
9 short steps. See your result before you share an email.
Questions
Questions we get about mobile apps
Why React Native rather than fully native apps?
One codebase across both platforms, with a consistent interface, is a better use of the budget for most products. When a feature genuinely needs native capability, that part is written natively.
Can you build P2P crypto trading apps?
Yes, including multilingual interfaces and escrow. In practice a P2P trading app is an escrow and dispute system with a mobile interface attached, and we scope it that way.
Do you handle app-store submission?
We prepare the app for store review: release builds, account deletion, a reviewer account and the listing details.
Do you build the backend too?
Yes. The API, database, admin panel and wallet services are often most of the work. See Backends & APIs.
Backends & APIsThree ways to start
Planning a mobile app?
Pick whichever suits you. A person reads every message.