Challenge
A payments startup needed PCI-aware architecture, fraud-resistant UX, and audit trails before launch partners would sign.
Case study · 2025
FinTech & Digital Payments
Secure digital wallet engineered for trust
FlutterNestJSAWSApplication SecurityCI-based TestingUnit/UI/Integration Testing
Client
Digital payments startup
Engagement
Flutter wallet · secure ledger
Duration
11 months
Year
2025
PayGrid Wallet was engineered for partner trust: double-entry ledgers, threat models, biometric auth, AWS infrastructure, and CI security gates. Fraud rules and observability were designed before launch — not bolted on after a questionnaire failed.
A Flutter wallet with NestJS ledgers, AWS infrastructure, and application security baked into every release.
Narrative
How the engagement moved from constraints to a shippable system.
Approach
We designed double-entry ledgers, threat models, encrypted at-rest patterns, and CI security gates with automated tests.
Solution
PayGrid Wallet ships with biometric auth, instant transfers, and observability suited for regulated reviews.
Scope
What we delivered
Flutter wallet for Android and iOS
NestJS ledger services with double-entry posting
Biometric auth and encrypted-at-rest patterns
Fraud rules engine with real-time flags
AWS infrastructure with security baselines
Full regression suite in CI
Highlights
What stood out
Partner security questionnaire cleared
Fraud rules with real-time flags
Regression suite on every PR
Launch-ready observability for regulated reviews
Engagement flow
A repeatable rhythm from discovery through hardening — tuned to this product’s constraints.
01
Threat & ledger design
Modeled threats, ledger invariants, and partner questionnaire gaps.
02
Core build
Shipped Flutter UX and NestJS ledger with security reviews.
03
Fraud & CI gates
Implemented fraud rules and automated security/test gates.
04
Partner readiness
Produced evidence packs and dry-ran audit walkthroughs.
Technology stack
The delivery stack behind this engagement — client surfaces paired with services, data, and infrastructure.
Frontend / Mobile
FlutterDartBiometric UXDesign System
Backend
NestJSNode.jsDouble-entry LedgerREST APIs
Cloud & Security
AWSApplication SecurityCI-based TestingEncryption
Outcomes
01
Partner security questionnaire cleared
02
Fraud rules engine with real-time flags
03
Full regression suite in CI on every PR
Looking ahead
Add multi-currency wallets and stronger device-binding options.
More work
Onboard the Apeiriion express
Tell us about your product, platform, or modernization goal — we'll assemble a senior squad and a clear delivery plan.