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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

    Serverless Full Stack Backend Software Engineer

  • Years of Experience

    6.2 years

Skillsets

  • GraphQL
  • Terraform
  • Serverless Framework
  • Rest APIs
  • React Native
  • react
  • RabbitMQ
  • OpenAI
  • Node.js
  • MySQL
  • MongoDB
  • Microservices
  • Jira
  • AWS
  • Git
  • Gemini AI
  • Express.js
  • DynamoDB
  • Docker
  • Cursor
  • Copilot
  • Cognito
  • Cloudfront
  • CI/CD
  • Bitbucket

Professional Summary

6.2Years
  • Jan, 2023 - Present3 yr 2 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

6.2Years

Backend Software Engineer

WithU
Jan, 2023 - Present3 yr 2 months
    Designed and scaled a serverless backend using AWS (DynamoDB, GraphQL, Cognito), achieving 99% uptime and supporting thousands of concurrent users. Optimised serverless scaling and load balancing, improving throughput by 30% and reducing latency by 20% during peak traffic. Reduced communication latency from 200ms to <5ms by developing a custom LAN WebSocket server, cutting infrastructure costs to zero. Implemented a cache layer in Node.js to reduce REST API calls by 30%, improving overall application performance and minimising incoming payload size. Automated CI/CD pipelines with AWS CodePipeline, reducing deployment time by 40% and enabling bi-weekly releases. Enhanced frontend performance by 25% using CloudFront caching, image compression, and optimised content delivery. Got Best Employee of the Quarter Award for the Mvmnt project in July 2024.

Backend Engineer

Diagnal Technologies
Jul, 2022 - Jan, 2023 6 months
    Developed scalable serverless features enabling 40% faster data retrieval. Implemented VTL resolvers for GraphQL queries, reducing compute time by 40%. Solved AWS Lambda cold-start issues with a warm-up strategy, reducing response times by 80%. Collaborated with DevOps to enhance deployment reliability through CI/CD automation.

Backend Engineer

Alter.Game
May, 2021 - Jun, 20221 yr 1 month
    Led backend development using Colyseus and Socket.IO, ensuring real-time synchronisation for thousands of concurrent players. Designed REST APIs for game score and history management, improving response time by 25%. Integrated Web3 SDK for crypto transactions (tokens, NFTs) and secure wallet payments. Mentored 2 junior engineers on scalable backend design and database optimisation.

Full Stack Developer

LeagueX Gaming
Feb, 2019 - May, 20212 yr 3 months
    Built an admin dashboard (Node.js, Express) that reduced manual processes by 40%. Integrated fantasy football features in React Native, increasing active revenue streams. Refactored UI with React, improving load time by 60% and reducing bugs by 15%. Deployed a user survey system for feedback, boosting engagement insights by 35%.

Education

  • Post Graduate Programme in Full Stack Engineering

    Birla Institute of Technology and Science (2021)

  • M.Sc. in Software Systems

    Kongu Engineering College (2019)