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NextIn Wallet

Production Web3 Wallet Platform

Role:
Sole Backend Engineer

Duration:
2025-2026

Designed and developed the backend architecture for a production-ready Web3 wallet platform integrating blockchain services, payment providers, KYC verification, real-time communication, and secure authentication into a scalable backend ecosystem.

70+ APIs13 Data Models5+ IntegrationsProductionWeb3

The Challenge

NextIn required building a secure backend ecosystem that connects traditional financial services with blockchain technology.

The platform needed to handle wallet operations, transactions, payments, identity verification, and real-time communication while maintaining security and scalability.

Multiple third-party integrations had to work together through a clean architecture that supports future Web3 expansion.

My Responsibilities

Key areas I owned as the sole backend engineer.

Backend Architecture

Designed the backend structure and organized business logic into scalable modules.

Node.jsExpressREST API

API Development

Built and maintained 70+ REST APIs covering authentication, wallet operations, transactions, and platform services.

RESTExpressValidation

Authentication & Security

Implemented secure authentication flows using JWT and Role-Based Access Control.

JWTRBACAuthorization

Database Design

Designed 13 MongoDB models to support users, wallets, transactions, and business workflows.

MongoDBSchema DesignIndexes

External Integrations

Integrated payment providers, blockchain services, and identity verification solutions.

MoonPayNowPaymentsOnfido

Realtime & Automation

Implemented realtime communication, notifications, and automated background workflows.

Socket.ioFirebaseCron Jobs

Architecture

Backend architecture showing core services, integrations and infrastructure layers.

ClientCore ServicesExternal IntegrationsInfrastructureNextIn Wallet — Backend ArchitectureClient AppsWeb / MobileExpress APIREST GatewayAuthenticationJWT + Passport + RBACWallet CoreTransactionsUser ServicesProfiles + KYCReal-timeSocket.ioWeb3BSC Smart ContractsPaymentsMoonPay / NowPaymentsIdentityOnfido KYCNotificationsFirebaseMongoDB13 Data ModelsBackground JobsCron + Email Scheduling

Engineering Highlights

✓Built 70+ production REST APIs
✓Designed 13 MongoDB data models
✓Implemented JWT authentication with RBAC
✓Integrated Web3 and Smart Contract services
✓Integrated MoonPay and NowPayments payment solutions
✓Implemented Onfido KYC verification
✓Built Socket.io realtime communication
✓Implemented Firebase notification workflows
✓Created automated background jobs using Cron

Technology Stack

Node.jsExpress.jsMongoDBJWTSocket.ioFirebaseWeb3.jsSmart ContractsMoonPayNowPaymentsOnfidoNode Cron

Key Outcomes

  • Designed a production-ready backend architecture
  • Delivered 70+ scalable REST APIs
  • Built secure authentication and authorization systems
  • Integrated financial and blockchain services
  • Created realtime communication workflows
  • Automated recurring platform operations