Rajnish.
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Lead Software Engineer · New Delhi

Rajnish
Kumar.

I build systems that scale, and teams that do the same.

Building systems that outlast their first sprint.

Writing about engineering.

Mentoring engineers who'll outgrow me.

Rajnish Kumar — Lead Software Engineer

"I don't really care which language you use."

What I care about: that the system survives its second year. That the team who inherits it can reason about it at 2 AM. That we shipped on time and didn't create a problem that takes three engineers six months to untangle.

The interesting problems are almost never about the technology. They're about constraints, tradeoffs, and the people who have to live with the decisions you make.

Numbers That Matter

Real results,
not estimates.

0+

Years building software

Across startups, agencies, and enterprise systems

0+

Engineers mentored

Through architecture discussions, code reviews, and career growth

0%

Drop in transaction times

Flipkart Health Plus API redesign

0%

More bugs caught pre-production

Automated validation framework for NVIDIA

0%

Increase in user growth

Taxspanner platform modernization

How I Approach Engineering

Six things I actually believe.

01

Start with the problem, not the stack

The framework you pick rarely makes or breaks a project. What actually matters is understanding your real constraints early on. I have watched teams succeed with Node, Python, and PHP, and I have seen them fail with all three when they solved the wrong problem.

02

Make complexity earn its place

Every extra layer is a cost someone on your team will have to pay later. A queue makes sense when you need async processing, not because it looks good in an architecture diagram. Add moving parts only when the problem leaves you no choice.

03

Code is read much more often than it is written

Write code for the person who has to debug an issue at 2 AM. That means straightforward naming, honest comments when something is tricky, and error messages that explain what broke instead of failing silently.

04

Speed is part of user trust

Dropping latency from 3.5 seconds down to 500 milliseconds is not just a tidy benchmark. It stops users from bouncing and getting frustrated. Measure before you guess, and fix the actual bottlenecks.

05

Leave teams stronger than you found them

Repositories get rewritten, but good engineering habits stick around. The most rewarding part of any lead role is helping team members build the skills and confidence to solve hard problems on their own.

06

Migrations are careful surgery, not quick tasks

Upgrading a live financial system from Python 2.7 to modern Python without downtime takes patience. You have to plan for failures, route traffic gradually, and verify every step along the way. Small incremental rollouts beat all-at-once cutovers every single time.

Career

Where I've worked,
and what I built there.

Context & Scope

Operating in a high-caliber consulting and technology services environment requiring dual focus: executing mission-critical engineering for global enterprise clients while building team technical capability and raising our internal delivery bar.

Client Engagements

NVIDIA (Current):Spearheaded development of a Python-based testing and benchmarking framework for validating hardware across multiple platform configurations, catching 35% more failures before production. Developed telemetry collection and debug data decoding tools.
Taxspanner:Led the migration of a production fintech platform from Python 2.7 and Django 1.6 to Python 3.10 and Django 4, introducing FastAPI microservices. Rebuilt backend services in the cloud, helping drive 40% growth in user acquisition without downtime.
Flipkart Health Plus:Built backend microservices for core commerce flows (cart management, payment refunds, coupon validation) and redesigned data access patterns, cutting transaction processing times by 70%.

Internal Leadership & Engineering Culture

Mentorship & Team Growth:Mentored a team of 10+ engineers through regular code reviews, architecture discussions, and career guidance, helping engineers level up their technical ownership.
Technical Hiring:Ran technical interviews and shaped the hiring bar for backend and full-stack positions, from initial screening through final technical rounds.
Engineering Standards:Established practical engineering standards that stuck: system design patterns, rigorous code review workflows, ethical AI developer tooling, and automated CI/CD pipelines.

Measurable Impact

NVIDIA: 35% more edge-case bugs caught before production. Taxspanner: 40% growth in user acquisition after modernizing. Flipkart Health Plus: 70% reduction in transaction processing times.

PythonFastAPIDjangoNode.jsReactMicroservicesPostgreSQLRedisDockerCI/CDAWSGCP

Beyond the Code

The person
behind the PRs.

I am a lead software engineer based in New Delhi. Over the last nine years, I have worked on web applications and distributed systems for early-stage startups and larger companies like NVIDIA and Flipkart.

I began as a full-stack engineer building student portals and recruitment sites. Over time, my focus shifted toward backend architecture, database performance, legacy migrations without downtime, and helping engineering teams work well together. At Prismberry, I split my time between technical design and implementation for our clients, while mentoring engineers and refining our development workflows.

I do not believe framework debates are all that important. What really matters is understanding the problem and its constraints clearly enough that the right technical choice becomes obvious.

Lightning Round

Mac or Linux?

Linux all the way

Tabs or spaces?

Tabs, Indentation Matters.

Monolith or microservices?

Monolith until you actually need separate services.

Coffee or tea?

Strong tea, But let me make it

Editor?

VS Code, and Vim when I am in a terminal.

Debugging style?

Logging first, then the debugger, never guesswork.

Best part of engineering?

Seeing an engineer you helped guide solve a tough challenge on their own.

Biggest pet peeve?

A one-hour meeting that could have been a short README.

Currently Exploring

What I'm focused on now.

Updated August 2026

Building

  • A Python test and benchmarking framework for validating NVIDIA hardware configurations.
  • Lightweight telemetry collectors to make distributed backend debugging simpler.

Exploring

  • Practical LLM evaluation techniques to verify if model prompts are genuinely improving on specific tasks.
  • Where AI code review tools save time versus where they introduce silent blind spots.

Reading

  • Designing Data-Intensive Applications by Martin Kleppmann (re-reading it with a few years of production scars makes it hit differently).
  • The Staff Engineer's Path by Tanya Reilly, a grounded look at senior technical leadership.

Thinking About

  • Balancing hands-on architecture work with giving senior engineers the room to own technical outcomes.
  • Writing clear engineering notes that explain the tradeoffs we made, rather than just the final success.