Vaultex
Full-stack transaction app with idempotency-aware mutex locking, TOCTOU concurrency debugging, interactive labs, and Auth Service integration.
Backend Engineer
Building APIs, authentication systems, and payment workflows with Node.js & AWS

Hi, I'm Lakshay — a Backend Engineer focused on building reliable systems.
I specialize in authentication architecture, payment integration, and event-driven services using Node.js, Express, MongoDB, and AWS.
My approach: understand the root cause, design clear architecture, implement with proper observability.
Engineering case studies — technical decisions, tradeoffs, and debugging stories.
Full-stack transaction app with idempotency-aware mutex locking, TOCTOU concurrency debugging, interactive labs, and Auth Service integration.
Centralized platform for managing resource links with pre-signed URL uploads and Auth Service integration.
Centralized authentication with asymmetric JWT, public key endpoint for local token verification, PostgreSQL, Google OAuth, and async AWS email delivery.
Centralized platform for capturing product ideas and thoughts, with soft delete and Auth Service integration.
Where I've applied backend engineering in production.
Backend Engineer
Backend systems powering event registration platforms, authentication, payment workflows, and administrative tooling for real users.
At InternWare, I worked on authentication, payment workflows, coupon management, and admin tooling for production event-registration systems handling real users and transactions.
Read full experience →Technical insights on web security, authentication, and modern software engineering
How payment gateway architecture evolves from insecure client-side flows to server-side order creation, webhooks, and reconciliation — and how we applied it at Internware.
Reflections from building my first AI application and learning what it really takes to ship production-ready AI — guardrails, human-in-the-loop, context management, and the difference between SDKs and Agent SDKs.
Learn why single long-lived tokens create UX and security problems, how access and refresh tokens solve them, and the key implementation decisions you need to make.
Open to Backend Engineer opportunities in authentication infrastructure, payment systems, or distributed services. Reach out via email or connect on social platforms.
dev@lakshaymahajan.com