SUMIT22 / PORTFOLIO

application architect, saas & fintech

Sumit Kumar

I design systems that move money and keep an exact record of it. 14+ years in software engineering, 9 of them in architect and lead roles across banking, payments, cards and crypto.

I take systems from requirements to production: working with business and client stakeholders, choosing the architecture and stack, designing components and AWS infrastructure, and writing the specs teams build from. Based in Bengaluru.

LinkedIn profile ↗

SutraOS CURRENT

Sep 2025 – present

Founder & Principal Engineer

sutraos.com ↗autopilotvideos.com ↗

Multi-tenant SaaS and AI products, designed and run end to end

Sole architect and engineer for live products, owning design, delivery, operations and AWS cost. NVIDIA Inception member.

SUTRAOS · MULTI-TENANT B2B SAAS

Modular monolith of 17 DDD modules that talk only through queued events or published interfaces, so any module can become its own service without a rewrite
Subdomain multi-tenancy with isolation enforced twice, at the gateway and in the application layer, so one bug can't expose another tenant's data
Architecture rules (module dependencies, API contracts, latency budgets, secrets handling) run as CI tests that fail the build

SALONOS · WHITE-LABEL BOOKING PLATFORM

Booking engine with multi-staff conflict detection, RFC 5545 recurrence and IANA time zones, shared by online and walk-in bookings
Payments on a PCI DSS SAQ-A model: no card data on our servers, signed webhooks, three levels of duplicate-payment protection

AUTOPILOT VIDEOS · AI SHORT-FORM VIDEO

Turns headlines or any URL into narrated YouTube Shorts: Gemini and Claude scripting, pluggable text-to-speech, Remotion and FFmpeg rendering
Publishes on a schedule through the YouTube Data API with KMS-encrypted tokens

BlackLine

Dec 2024 – Sep 2025

Senior Software Engineer

High-volume financial data pipeline for enterprise customers

Owned core components processing invoices, account data and statements.

ARCHITECTURE

Moved stage-to-stage processing onto AWS SQS so each stage scales and fails independently
Led batch processing and XML transformation workflows in Symfony and MySQL, improving throughput and reliability
Ran design reviews on service boundaries, event contracts and domain models; fixed vulnerabilities with the security and platform teams

Open Financial

Jan 2023 – Apr 2024

Lead Software Engineer

20–50x faster production APIs, and a bank platform delivered

Neobanking platform serving hundreds of thousands of API requests a day.

RESULTS

Cut critical API response times by 20–50x; the cause was controllers with 20–30 injected dependencies, fixed with a SOLID refactor and verified with APM p95/p99 data and load tests
Designed and delivered a NestJS identity and authentication microservice used by multiple internal platforms, and owned its API contract
Led a team of 5 and gathered requirements directly from HDFC Bank; delivered their business banking admin platform under bank security and compliance requirements

Spenmo YC S20

Sep 2020 – Nov 2022

Lead Architect

Multi-currency payins, payouts and card issuing

Corporate cards and expense management across several countries.

PAYMENTS & CARDS

Architected a multi-currency, multi-country PayIn and Payout system for partners
Led the Cards team (3 developers) and delivered self-serve virtual and physical card lifecycle management
Owned the MatchMove and Rapyd integrations: APIs, webhooks and reconciliation
Turned regulatory requirements into system designs with Product, Operations and Compliance; added centralised logging and alerting that cut incident response time

Unocoin

Jan 2017 – Aug 2020

Web Architect

Modernising and scaling a crypto exchange

Took the exchange from a legacy PHP application to a multi-country platform. Led a team of 7.

ARCHITECTURE

Migrated legacy PHP to Laravel with standardised REST APIs, redesigned the MySQL schema and added Firebase real-time data
Re-architected for multiple countries (currencies, languages, KYC rules, time zones), with configurable KYC that adds documents without app releases
Designed AWS infrastructure (VPC, EC2, Auto Scaling, IAM) and moved heavy work onto SQS to absorb spikes during market volatility

Earlier roles

Oct 2010 – Jan 2017

HolidayIQ, HeadHonchos, others

Search, ranking and growth engineering

HIGHLIGHTS

HolidayIQ: Solr schemas and APIs for hotel, blog and geo-spatial search, plus a system that flagged plagiarised reviews and suspicious review activity
HolidayIQ: hotel ranking over user ratings for thousands of hotels, and Google Vision image tagging for landmarks and moderation
HeadHonchos (ABC Consultants): LinkedIn application parsing that drove over 30% of monthly sign-ups

things I've built in public

Open source

sendrail

TypeScript · AWS SES

Email deliverability on your own AWS SES account: sending, delivery feedback, suppression and reputation. It's the layer you'd otherwise rent from an email provider, so the domain reputation stays yours. Express and NestJS adapters.

View repository ↗

FindMyStar

Rust · React Native

Offline mobile app that points an AR arrow at any of ~620 stars, planets and deep-sky objects. Positions are computed in Rust against VSOP87 and Hipparcos data and validated against USNO and JPL Horizons. No network calls, no data collected.

View repository ↗

time-travel-carousel

TypeScript · React

A React carousel where every slide has a version history: left and right move between items, up and down move through revisions. Loads files through your own authenticated client; zero runtime dependencies.

View repository ↗

how I approach slow or fragile systems

Writing

32 MINUTES TO 2 MINUTES

Rewriting a Symfony integration suite in one PR: 684 tests became 881, the run dropped from ~32 minutes to 2 minutes 10 seconds, and three production bugs surfaced along the way. False starts included. Read the write-up ↗

polyglot, mostly PHP and TypeScript in production

Stack

languages: PHP, TypeScript, JavaScript, Go, Java
frameworks: Laravel, Symfony, NestJS, Express, Next.js, React, React Native
data: PostgreSQL, MySQL, Redis, MongoDB, Apache Solr
cloud: AWS (EC2, S3, SQS, SNS, SES, IAM, VPC, Auto Scaling), Docker, GitHub Actions, Jenkins
practice: Domain-driven design, event-driven architecture, multi-tenant SaaS, legacy modernisation
compliance: PCI DSS (SAQ-A), GDPR, RBI and banking requirements

Hiring an architect?

I'm open to Application Architect, Solution Architect and Lead Engineer roles in fintech or SaaS, in Bengaluru, Mumbai, the UAE or remote. Also available for architecture reviews and technical due diligence.

$ open https://www.linkedin.com/in/sumit22