Rahul Sinha

Hello I'm

Rahul Sinha

Tallinn, Estonia

"I design and build real-world applications — turning complex problems into scalable, user friendly systems, and shipping them fast."

Typescript

Javascript

Nodejs

Nextjs

React

MongoDB

Express

Redux

HTML

CSS

Sass

React Native

C++

Bitcoin

Linode

Retool

Mixpanel

My experience

Bringin

Founding Engineer

Founding Engineer at @Bringin

Oct 2022 - Present

Built and scaled a production fintech platform serving 10,000+ users, supporting Bitcoin-to-EUR transactions, KYC onboarding, debit cards, and payment workflows across web and mobile using React, Next.js, Node.js, MongoDB, and Redis.
Reduced production issues by 50–60% by analyzing support tickets, PostHog analytics, and transaction failures, implementing fixes across frontend, backend, and operational workflows to improve reliability and user experience.
Improved onboarding and transaction performance, reducing page load times from ~10s to 3–4s through API orchestration, async state optimization, and rendering improvements.
Architected and implemented secure authentication using OAuth (Google/Apple) with a Backend-for-Frontend (BFF) layer, enabling cross-subdomain session management and improved security.
Designed and implemented payment systems supporting Lightning and on-chain Bitcoin transactions, including state tracking, retries, failure handling, and reconciliation across external providers.
Built and maintained onboarding, authentication, and KYC systems integrating third-party providers, handling complex async workflows, compliance states, and provider-specific edge cases.
Developed observability and debugging infrastructure using centralized logging, Slack alerts, and global error handling to improve incident response and production visibility.
Built internal tooling for transaction monitoring, reconciliation, customer support workflows, and operational visibility.
Managed production and sandbox deployments across Vercel and cloud environments, including NGINX configuration, Cloudflare setup, webhook routing, and cross-service integrations.
Collaborated directly with founders, mobile engineers, and external providers to shape product, architecture, and operational decisions.
Leveraged AI-assisted development workflows to accelerate debugging, delivery, and iteration across complex fintech systems.

What I do

Engineering

Architecting scalable frontend systems (Next.js, React, Redux)
Designing backend APIs and data models (Node.js, TypeScript)
Building real-time systems (WebSockets, event-driven flows)

Product & System Thinking

Designing end-to-end product flows from idea to production
Handling complex async systems (payments, retries, failures, state transitions)
API orchestration and distributed data flow design
Debugging and stabilizing production systems

Systems & Infrastructure

Deploying and managing production applications (NGINX, servers, environments)
Performance optimization and system reliability
Handling integrations with external services and APIs

Execution

End-to-end feature ownership
Rapid iteration and shipping
Translating product requirements into scalable systems
AI-assisted development for faster and more reliable delivery

My latest work

Live on Mac App Store (Testflight)

Privacy-first macOS app that detects real blink behavior using on-device computer vision — shipped to the App Store with real-time feedback loops for digital eye strain.

Shipped a privacy-first macOS app with real-time CV pipeline and deterministic, testable architecture

Built blink detection using EAR with pose normalization and adaptive thresholds

Designed system architecture, UX, and validation layers while leveraging AI tools to accelerate implementation

Solved CV challenges like false positives, drift, and frame-processing bottlenecks

Implemented closed-loop UX (nudges + blink-to-dismiss) for behavioral correction

Released on the Mac App Store with TestFlight rollout and an automated CI release pipeline

Owned product decisions end-to-end (UX, architecture, validation, and release pipeline)

Swift

SwiftUI

AVFoundation

Vision

CoreML

AppKit

National Hackathon Winner

End-to-end AI system that converts healthcare PRDs into structured, exportable test cases — reducing manual QA effort.

Built a production-ready AI workflow that judges could run end-to-end (not just a demo)

Built multi-stage pipeline for document parsing → AI generation → validation → Jira export

Hardened LLM output with JSON schema validation, parsing fallbacks, and deterministic ID generation for retries

Designed a state-driven review UI for the approval lifecycle (draft → reviewed → approved → exported)

Implemented Jira OAuth with token refresh and bulk issue creation with per-row failure isolation

Cut serverless cold-start cost via token caching and Vertex/Jira client reuse across invocations

NextJS

TypeScript

Vertex AI

Document AI

Jira API

GCP

Achievements

National Hackathon Winner

1st Place — Gen AI Exchange Hackathon (270K+ participants)

Google Cloud × Hack2Skill · 2025

View official event

Won 1st place among 270,000+ developers by building a production-ready AI system for automated test case generation.

4,457+ working prototypes submitted

Selected among top 100 teams for final offline demo

Evaluated by 30+ industry experts (Google, NASSCOM, enterprise partners)

Built a fully functional end-to-end system (not just a prototype)

Focused on real-world deployment, scalability, and enterprise integration — not just model output.

Final demo day — presenting to Google Cloud & industry jury

Ready to start
your next project?
Let's talk about it!