Hello, I'm

Sahiljeet Singh Kalsi

Software Engineer

Software engineer working on backend systems and infrastructure for production-scale applications. Primarily working with Node.js, TypeScript, NestJS, PostgreSQL, Redis, and AWS to build scalable APIs, distributed services, and real-time systems. I work on performance optimization, database-heavy workloads, infrastructure reliability, and backend architecture improvements across multiple microservices. worked on reducing backend CPU utilization from ~99% to ~25%, rebuilding a large FFmpeg-based transcoding pipeline, and migrating services from GCP to AWS. I enjoy understanding system bottlenecks, improving performance under load, and building backend systems that remain reliable at scale.

cut in backend CPU usage

microservices migrated to AWS

0k+

concurrent users served

My Work: Senior Full-Stack Developer at Newral - Build scalable backend systems, infrastructure, and distributed services for production applications serving 100,000+ concurrent users.

Open to software engineering opportunities involving distributed systems, infrastructure, and scalable application development.

Experience

Senior Full-Stack Developer

Present

Synappses

Building Synapse (synappses.in / synappses.live), a multi-tenant LMS and creator platform for EdTech businesses to sell courses and engage their audience. Live and onboarding pilot clients.

Building the platform with NestJS, TypeScript, Prisma, and React.
Own architecture decisions for a multi-tenant system serving multiple EdTech businesses from a single codebase.

Full-Stack Owner

Sept 2025 - Present

Competishun (via Newral)

Own full-stack development for Competishun, a large-scale EdTech platform for JEE/NEET aspirants with 100,000+ active users, serving students concurrently across a ~9-microservice architecture.

Reduced backend CPU usage from ~99% to ~25% through SQL query optimization, Redis caching, and workload restructuring.
Redesigned the video upload and transcoding pipeline using FFmpeg, achieving over 80% faster video processing.
Led the migration of 9 microservices from GCP to AWS, improving scalability, reliability, and cost efficiency.
Optimized infrastructure footprint, reducing compute usage from 32 cores to 4 cores.
Resolved critical production issues across multiple microservices, leading to a ~90% reduction in app crashes.

Backend Owner (Client Project)

Newral client work

Upto

Built the backend for Upto, a social media application for a US-based client, designing scalable APIs and data models end to end.

Designed and built the entire backend solo with NestJS, TypeScript, Prisma, and PostgreSQL.
Modeled the core social data layer (feed, relationships, content) for scale from day one.

Backend Developer

Newral client work

US-based startup (Newral client work)

Developed a scalable real-time backend for a separate US-based startup client.

Built with Node.js, Express, Redis, and WebSockets for real-time communication at scale.

Process & Tooling

Ongoing

Cross-cutting, across all of the above

Set up delivery and quality infrastructure alongside feature work.

Set up CI/CD pipelines with GitHub Actions and unit/integration test suites.
Used AI-assisted development tools - GitHub Copilot, Claude Code, Antigravity, Cursor, and custom AI agents - to speed up delivery.