Fintech Mobile App Backend Development

Senior Backend Engineer (10–15 Day Delivery) — Microservices, MySQL/Postgres, MongoDB, Firebase Auth: Project Summary

We’re building a production-ready backend for a consumer fintech-style mobile app.
You’ll deliver one main backend service and one SMS-processing microservice, both built for scale, clean architecture, and high performance.

This is a fast-track 10–15 day engagement.
Only apply if you’re confident delivering polished, testable, and deployment-ready code within this timeline.

What You’ll Build

1. Main Backend Service

A modular backend with:
Firebase + JWT authentication
User profile module
Rewards module
KYC flow
Integration with a third-party gold provider (similar to Augmont)
Buy/sell
Goal/SIP management
Withdrawals
A full relational database architecture using MySQL or Postgres
A clean business logic layer with separation of concerns
A double-entry ledger system
API documentation (OpenAPI/Swagger)

2. SMS Processor Microservice
A separate service responsible for:
Pulling SMS data from the mobile app
Parsing and categorizing messages
Storing raw, processed, and categorized results in MongoDB
Handling sync, deduplication, and incremental updates
Notifying the main backend when results are ready
Optimized for high-volume SMS processing

Technical Requirements:

You must be comfortable with:
Node.js / NestJS / FastAPI / Go (any modern backend framework)
MySQL or Postgres
MongoDB
Firebase authentication
Event-driven communication between microservices
Redis caching
Queue systems (SQS, RabbitMQ, or similar)
Writing clean, testable code
Designing efficient database schemas
Building APIs meant for 10–50k users
Ensuring <300ms P95 API responses for standard calls
Handling large SMS datasets (tens of thousands per user)
Performance Expectations

The delivered system must handle:

1k requests/min on the main backend without errors
10k SMS/min ingestion on the microservice
1–2M ledger rows in the database
Zero duplicate SMS entries
Fast incremental sync for new SMS
Stable and predictable behavior under load


What We’re Looking For

Experience in fintech or financial data handling
Strong in database design and optimizations
Experience with microservices and event-driven architecture
Ability to deliver fast without compromising stability
Strong communication and daily progress updates

Nice to Have
Experience with gold trading platforms or wallet systems
Experience in SMS processing or NLP
Cloud experience (AWS preferred)