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SKSachin Kumar

Sachin Kumar, software engineer: I build software that holds up in production.

I'm Sachin Kumar, a software engineer who works across the stack - scalable backend services in Go and Node.js, and fast, polished interfaces in React and TypeScript.

See my workGet in touch
Portrait of Sachin Kumar

Building with

Go · TypeScript · React

Building and running production software
2+ yrs
Projects shipped end to end
15+
LeetCode contest rating
2000+

About

Engineer first, details obsessive.

I'm a software engineer who enjoys owning a problem end to end - from designing the API and data model, to the services that run it, to the interface people actually touch. Lately that's meant systems where money moves - where every rupee has to land in the right place, exactly once, even at scale.

I'm drawn to the unglamorous parts that decide whether software holds up: edge cases, retries, idempotency, and the event-driven plumbing between services. Most of my work is in Go, TypeScript and React, and lately I've been building with LLM APIs too.

Years of competitive programming shaped how I think about correctness and performance. Outside of work you'll usually find me on a cricket field or deep in a playlist.

Now
SDE-1 at smallcase
Focus
Backend systems & full-stack product
Education
B.Tech, IIIT Ranchi - 2025
Off the clock
Cricket, music & contest problems

Toolkit

  • Languages
    GoTypeScriptJavaScriptPythonC++
  • Backend
    Node.jsREST APIsMicroservicesWebSocketstRPCPrisma
  • Frontend
    ReactNext.jsTailwind CSSReduxZustandFramer Motion
  • Data & messaging
    PostgreSQLMongoDBRedisSQLiteAWS SQS
  • Cloud & tooling
    AWSDockerLinuxNginxCI/CDVercel
  • AI
    LLM APIsRAGAI agents

Experience

Where I've shipped.

The companies I've worked with, and what I owned at each.

smallcase

Credit team · Hybrid

  1. Software Development Engineer 1

    May 2025 - Present
    • Integrated a new lending partner end-to-end - API contracts across microservices through to SQS-backed webhook processing - bringing loan disbursal turnaround under 30 minutes.
    • Built an event-driven delayed-processing pipeline for lender webhooks that were silently dropping on edge cases, eliminating 20+ failures a week with no manual intervention.
    • Added a reconciliation layer that predicts and validates loan amounts before submission, closing the market-value drift between pledge and disbursal behind 30+ rule-engine rejections a week.
    • Traced 60% of pledge drop-offs to eligibility edge cases and redesigned the journey with a graceful fallback, so users continue with a reduced amount instead of hitting a dead end.

  2. Software Engineer Intern

    Aug 2024 - Apr 2025
    • Shipped a self-serve dashboard giving 200+ lending partners real-time loan status - cutting their inbound calls to operations by 95%.
    • Fixed duplicate EMI debits by decoupling principal and interest collection in the repayment flow, reducing related support queries by 80%.
    • Rebuilt the loan servicing dashboard to cover 50+ disbursement scenarios across demat and non-demat funds, turning support tickets into self-explanatory UI.
    • Built KYC onboarding flows to lender compliance standards, with fallbacks for DigiLocker failures and PAN mismatches so users never stall mid-onboarding.
GoTypeScriptReactAWS SQSMicroservices
Utsav

Remote

  1. Full Stack Developer Intern

    May 2023 - Aug 2023
    • Rebuilt the event registration flow in Next.js with fewer steps, increasing completed registrations by 20%.
    • Redesigned the admin portal around a timeline-based shipment view, cutting time spent on routine admin tasks by 30%.
    • Standardised the shared component library so new screens shipped visually consistent by default.
Next.jsReactNode.js

Projects

Things I've built on my own.

Side projects where I explore real-time systems, concurrency and AI - each one shipped end to end.

More on GitHub
Auction Table screenshot

Auction Table

2024

Real-time auction platform. Bids are broadcast to every bidder over WebSockets and written inside MongoDB transactions, so concurrent bids on the same lot can never race each other.

Next.jsSocket.ioNode.jsMongoDBshadcn/ui
Live site Source
Document Buddy screenshot

Document Buddy

2024

Upload any PDF and ask it questions in plain language. Type-safe end to end with Next.js, tRPC and Prisma.

Next.jsTypeScriptTailwind CSStRPCPrisma
Live site Source
PublicMart screenshot

PublicMart

2023

Full-stack e-commerce store with product search, cart, reviews and Stripe checkout, backed by an Express and MongoDB API.

ReactNode.jsExpressMongoDBFirebase
Live site Source

Writing

Notes from building things.

I write about patterns I've used in production React and TypeScript codebases.

All posts on Medium

Open source

Contributing upstream.

@imsachin49

Contribution activity

Contact

Let's build something reliable.

Whether it's a role, a hard backend problem or just a chat about engineering - my inbox is open.

Email me LinkedIn

sachin.kumar05115@gmail.com

© 2026 Sachin Kumar. Built with Next.js & Tailwind CSS.