Hi, I am

Sanjay Kumar

Senior Backend Engineer

Senior Backend Engineer designing and scaling distributed systems for real-time, business-critical workflows.

Currently building a production-grade multilingual AI voice automation platform (Pipecat-based) integrating telephony, STT, LLMs, and TTS with advanced interruption handling and low-latency optimizations.

Experienced in architecting event-driven systems and real-time payment infrastructure handling ₹30Cr+ monthly transactions with 99.9% reliability.

Download Resume
smskumar515@gmail.com +91 9092701806 Chennai LinkedIn GitHub

Professional Experience

Senior Backend Engineer

Vegrow Chennai

Jul 2024 – Present
  • Architected and led a production-grade multilingual AI voice automation platform integrating Exotel, Deepgram, Sarvam, Gemini, OpenAI, and Cartesia via a 3-layer pipeline; handling 10K+ calls/day with ~0.7s avg response latency and 20 parallel channels; reduced operational load by 30%.
  • Implemented real-time orchestration (VAD tuning, interruption control, silent detection, low-latency filler injection) and function-calling + RAG workflows; improved CQS score by 25%.
  • Built and scaled real-time payment infrastructure supporting ₹30Cr+ monthly transactions at peak ~1K TPM with 99.8% reliability across Razorpay, HSBC, and ICICI (IMPS, UPI, NEFT); implemented idempotency, transactional locking, auto-retries, and secondary status checks.

Software Development Engineer

Vegrow Chennai

Apr 2023 – Jun 2024
  • Built a high-throughput Change Data Capture (CDC) microservice for a 17GB SQL database processing up to 10K events/sec; centralized real-time cache invalidation and event generation, eliminating cross-service invalidation logic.
  • Designed high-throughput notification systems (Slack, WhatsApp, Firebase) handling 10K+ messages per minute.
  • Integrated credit verification, KYC, and UPI/payment workflows, reducing onboarding time by 80% and improving payment lifecycle reliability.

Software Development Engineer

Xoxoday Bangalore

Jun 2021 – Mar 2023
  • Developed scalable backend services using AWS (Lambda, SQS, SNS, SES, DynamoDB, EventBridge) and event-driven architecture patterns.
  • Processed 200K+ reward transactions with 99.9% uptime; optimized job processing using Redis queues.
  • Contributed to Razorpay payment gateway integration, implementing API workflows for order creation, payment verification, webhook handling, and transaction status reconciliation.

Software Engineer Intern

Xoxoday Bangalore

Dec 2020 – May 2021
  • Contributed to backend microservices using Node.js and MySQL; supported production bug fixes and feature development.
  • Integrated third-party platforms (HubSpot, ZohoCRM, SurveyMonkey) to automate customer onboarding and workflow systems.

Backend Developer (Freelance)

Freelancer.com Chennai

May 2020 – Dec 2020
  • Designed and built a backend system for an online poker application using Node.js and MySQL, implementing game logic handling, secure transaction flows, and real-time table state management.
  • Built multiple small-use-case Flutter applications for clients using Firebase (Auth, Firestore, Cloud Functions), delivering end-to-end mobile solutions without a dedicated backend layer.

Software Engineer Intern

Virtusa Chennai

May 2019 – Oct 2019
  • Worked on microservice development and deployment using Node.js, Docker, Kubernetes, Istio, and GCP.
  • Assisted in containerization, CI/CD setup, and cloud-based service orchestration.

Selected Projects

Postman for AI Voice Agents

Feb 2026 - Present

Architected a modular three-layer voice AI pipeline (STT → LLM → TTS) using Python, FastAPI, and Pipecat. Built a zero-database, real-time testing sandbox enabling rapid prototyping and evaluation of Deepgram, OpenAI, Gemini, Cartesia, and Sarvam. Engineered a React + TypeScript dashboard with live audio visualizers and real-time observability.

Live View

My Funds

Dec 2025 - Feb 2026

Cross-platform personal finance application using React, TypeScript, Vite, and Firebase. Engineered a privacy-first, offline-capable voice transaction recorder. Integrated Google Gemini AI for personalized financial insights. Packaged as a PWA and native mobile app.

Live View

Food Ordering App - CASSIA

Aug 2020 - Nov 2020

Online food ordering app developed using Flutter & Firebase. It also has an integration with payment gateway (RazorPay) and wallet implementation.

Repository

Attendance App

Apr 2020 - May 2020

A mobile app developed with Flutter and Firebase to manage attendance, providing RBAC with different roles like staff, student, admin and also developed a dummy enrolment server with NodeJS.

Repository

Book_olx

Nov 2018 - Dec 2018

An android app for selling and buying used books inside a university and a NodeJS server for data management with MongoDB.

Repository

Facial Recognition System

May 2018 - Jun 2018

Built a prototype for an IoT enabled attendance management system for University hostel.

Repository

Technical Skills

Languages & Frameworks

Go (Primary)Node.jsRuby on RailsPythonTypeScriptExpress.jsHTML/CSS

Databases & Messaging

MySQLMongoDBKafkaRedis

AI Voice & LLM Systems

STT: Deepgram, SarvamLLMs: Gemini, OpenAITTS: Cartesia, SarvamFunction Calling & RAG PipelinesReal-Time Call Orchestration (Pipecat, VAD, interruption strategies)

Cloud & DevOps

AWSGCPDockerKubernetesJenkinsGitHub ActionsCI/CD Pipelines

Tools & Integrations

RazorpayTwilioExotelFirebaseHubSpotZohoCRMZapierSlackPostman

Testing & Monitoring

RSpecJestTestifyNew RelicCloudWatchSigNoz

Honors & Awards

Best Individual Contributor Award

Vegrow | 2025

Recognized for high-impact backend contributions across AI voice infrastructure, payment systems, and platform reliability initiatives.

Best Team Innovation Award

Vegrow | 2025

Awarded for architecting and delivering a real-time Instant Payment Service that became a key differentiator for the organization.

2nd Place – Vetechathon

Vegrow | 2024

Designed and presented a scalable backend architecture focused on automation and system efficiency under time constraints.

Education

M.Sc. Computer Science (Integrated)

College of Engineering, Guindy

Aug 2016 – Apr 2021 Chennai
CGPA: 8.6 / 10

Higher Secondary Certificate (HSC)

AMM School

Jun 2015 – Apr 2016
Percentage: 97.25%

Secondary School Leaving Certificate (SSLC)

AMM School

Jun 2013 – Apr 2014
Percentage: 93.6%