FinTech & AdTech
Flash Transfer
Cash and Crypto Conversion Platform
Secure digital-asset transfer platform enabling seamless conversion between cash and cryptocurrency
The problem
Converting between cash and cryptocurrency is where most users lose trust: rates move, settlement is opaque, and compliance requirements sit on top of everything. Sonex Digital needed a platform where conversion in either direction is fast, the rate and fee are visible before commitment, every transaction is traceable, and the system holds up under the security expectations of a financial product.
How we built it
6 decisionsBuilt a bidirectional conversion engine handling cash-to-crypto and crypto-to-cash flows with transparent rate and fee display before confirmation.
Implemented a transaction lifecycle with immutable audit logging across initiation, verification, settlement and completion.
Engineered security-first architecture: encrypted data at rest and in transit, hardened authentication, role-scoped access and anomaly monitoring.
Delivered user identity and verification workflows appropriate to a financial-services product.
Built administrative tooling for transaction oversight, exception handling, limits and reconciliation.
Structured the engagement on an incremental model so capability expands continuously against a live platform.
System architecture
6 layersEvery layer designed, built and operated for this system to run in production.
Frontend
React / Next.js with TypeScript
Backend
Node.js transactional service layer with idempotent operation handling
Database
Relational store for transactional integrity with strict consistency guarantees
Caching & Queues
Redis for rate caching, locking and asynchronous settlement jobs
Security
End-to-end encryption, secrets management, hardened authentication, full audit logging
Infrastructure
Cloud deployment with containerisation, CI/CD and monitoring
What was delivered
7 modules- 01
Conversion Engine
Bidirectional cash to crypto and crypto to cash conversion with live rate and fee transparency.
- 02
Transaction Lifecycle
Initiation, verification, settlement, completion and failure handling with audit trail.
- 03
Wallet & Balance Management
Asset balances, transaction history and statement generation.
- 04
Identity & Verification
User onboarding and verification workflow with document handling.
- 05
Security & Monitoring
Encryption, hardened auth, session control, anomaly detection and alerting.
- 06
Admin Console
Transaction oversight, limits, exception handling and reconciliation reporting.
- 07
Reporting
Volume, settlement and reconciliation reporting for operations and finance.
Outcomes
3 resultsFast, transparent conversion in both directions with rate and fee visible before commitment.
Full transaction traceability suitable for a financial-services audit posture.
Continuing in-service engagement under an incremental delivery model since early 2025.
Value delivered
For users: a reliable, transparent route between cash and digital assets.
For the client: a security-hardened platform that can scale transaction volume without re-architecture.
Client and product names are used with reference to publicly available product information. Engagement details covered by non-disclosure agreements are described at capability level only.