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Karthikeyan S

I am currently working as a Backend Software Engineer at WithU (UK), where I design and scale robust serverless architectures for a global fitness and wellness platform. My focus lies in delivering highly available and low-latency backend systems, leveraging AWS services to optimise performance and cost-effectiveness. I am known for owning end-to-end backend modules and have been recognised with the "Best Employee of the Quarter" award for delivering mission-critical features ahead of deadlines.

My expertise includes building scalable microservices with Node.js, TypeScript, and GraphQL, and deploying serverless infrastructures with AWS Lambda, DynamoDB, and Cognito. I’ve also worked on real-time multiplayer gaming platforms and fintech integrations using Web3 SDK and WebSockets. I’m experienced with CI/CD automation, REST APIs, MongoDB, Redis, React, React Native, and more – making me well-versed in full-stack as well as backend-heavy development.

Across roles, I have successfully led projects, mentored juniors, and collaborated closely with cross-functional teams using Agile methodologies. A proactive and fast learner, I consistently ensure quality and timely delivery. I’m now looking forward to new international opportunities—especially in Germany—where I can further challenge myself and make impactful contributions to innovative backend systems.

  • Role

    Senior Backend Engineer

  • Years of Experience

    7.17 years

Skillsets

  • Ethereum
  • react
  • React Native
  • Rest APIs
  • Serverless Framework
  • Terraform
  • Agile/Scrum
  • AppSync
  • Claude code
  • Colyseus
  • RabbitMQ
  • GCP
  • JavaScript
  • Monday
  • Next.js
  • Python
  • Redis
  • Socket.IO
  • TypeScript
  • Web3 sdk
  • Gemini AI
  • Bitbucket
  • CI/CD
  • Cloudfront
  • Cognito
  • Copilot
  • Cursor
  • Docker
  • DynamoDB
  • Express.js
  • AWS
  • Git
  • GraphQL
  • Jira
  • Microservices
  • MongoDB
  • MySQL
  • Node.js
  • OpenAI

Professional Summary

7.17Years
  • Jan, 2023 - Present3 yr 4 months

    Backend Software Engineer

    WithU
  • Jul, 2022 - Jan, 2023 6 months

    Backend Engineer

    Diagnal Technologies
  • May, 2021 - Jun, 20221 yr 1 month

    Backend Engineer

    Alter.Game
  • Feb, 2019 - May, 20212 yr 3 months

    Full Stack Developer

    LeagueX Gaming

Work History

7.17Years

Backend Software Engineer

WithU
Jan, 2023 - Present3 yr 4 months
    Led architecture and development of an AWS serverless backend with Node.js, TypeScript, GraphQL, and Cognito, embedding security, observability, and cost controls. Enhanced scalability via autoscaling, caching, and event-driven patterns, improving throughput by 30% during peak demand. Established CI/CD with automated testing and gated releases, accelerating delivery by 40% while reducing deployment risk. Defined and governed API contracts and service SLAs with Product and Frontend teams, successfully accelerating 5 major cross-team initiatives each quarter. Operationalized monitoring and on-call playbooks to sustain reliability at 99.9% uptime. Contributed to onboarding improvements associated with increased revenue opportunities.

Backend Engineer

Diagnal Technologies
Jul, 2022 - Jan, 2023 6 months
    Delivered serverless GraphQL APIs with AppSync, VTL resolvers, and DynamoDB following robust schema design and IAM policies. Implemented cold-start mitigation and warm-up strategies to improve response readiness by 65%. Strengthened CI/CD pipelines and release governance with automated checks and safe rollback paths. Drove cross-functional collaboration with DevOps and QA to uplift deployment consistency and platform resilience by 35%. Optimized request handling to achieve 50% latency reduction from 180ms to 90ms, delivering faster responses and improved user satisfaction across services.

Backend Engineer

Alter.Game
May, 2021 - Jun, 20221 yr 1 month
    Engineered real-time multiplayer backends using Socket.IO and Colyseus, ensuring consistent state and low-latency event handling. Built RESTful services with caching and optimized data flows, improving API responsiveness by 45%. Integrated Web3/Ethereum SDKs for wallets, tokens, and NFTs with secure signing and validation. Mentored 2 junior engineers through code reviews, pairing, and design guidance to raise code quality and delivery velocity. Led onboarding enhancements for the multiplayer backend, increasing new player signups by 18% in 90 days, driving stronger early retention.

Full Stack Developer

LeagueX Gaming
Feb, 2019 - May, 20212 yr 3 months
    Shipped full stack features across Node.js, Express, React, and React Native for web and mobile experiences. Delivered admin dashboards and workflow automation, saving 20 hours per week in operational effort. Refactored UI components and optimized API integration to elevate stability and page performance by 15%. Defined API standards for authentication, validation, and rate limiting, improving security posture and maintainability.

Major Projects

4Projects

Mail Wise AI-Powered Email Analysis

    Full-Stack Next.js application featuring a React UI and server-side API routes. Integrated Google's Genkit and Gemini models for AI-powered email validation, disposable provider detection, and fake email identification. Utilized Firebase Firestore to capture user leads and manage API access interest.

OpenClaw | Clio

    Engineered an AI-powered automation platform to manage a daily YouTube content pipeline using Claude, Veo 3.1, Hugging Face, Groq TTS. Built automated trend-ingestion pipelines from X (Twitter) and integrated real-time event distribution to Discord channels.

Mvmnt | WithU

    UK-based fitness and wellness app providing personalised workout experiences for thousands of users globally. Designed and scaled a serverless backend on AWS (DynamoDB, GraphQL, Cognito) achieving 99% uptime and supporting thousands of concurrent users.

Enhance | Diagnal Technologies

    UK-based streaming platform serving media enterprises across Asia with scalable content delivery. Implemented VTL resolvers for GraphQL queries that decreased compute time by 40%. Devised a warm-up strategy to mitigate AWS Lambda cold starts, reducing response times by 80%.

Education

  • Post Graduate Programme in Full Stack Engineering

    Birla Institute of Technology and Science, Pilani (2021)

  • M.Sc. in Software Systems

    Kongu Engineering College (2019)