Backend Engineer

Summary

John O, is a backend-focused Software Engineer with over seven years of experience building and scaling production-grade systems across fintech, SaaS, e-commerce, and API-driven platforms. He specializes in TypeScript, Node.js, NestJS, Python, and FastAPI, with strong expertise in designing RESTful and GraphQL APIs that serve thousands of concurrent users. His technical skill set spans cloud-native infrastructure and DevOps practices, including AWS and Azure services, Docker, Kubernetes, Linux, Nginx, CI/CD pipelines, and infrastructure-as-code using AWS CDK. John is highly experienced with relational and NoSQL databases such as PostgreSQL, MySQL, MongoDB, Redis, and vector databases, and has implemented event-driven and microservice architectures using RabbitMQ and Apache Kafka to improve performance and scalability. Beyond traditional backend engineering, he brings advanced experience in AI and robotics, working with RAG systems, LLM fine-tuning, AI/ML model training, ROS2, microcontrollers, and autonomous navigation systems. He has led cross-functional engineering teams, delivered multiple production systems, integrated secure payment platforms like Stripe and Paystack, and consistently builds reliable, scalable solutions with a strong emphasis on performance, security, and real-world impact.

Meet John O.

"Introduce Yourself"

"What are you looking for in your next opportunity?"

Assessment Scores

General Project Assessment

91%

Great score on Implement LRU Cache Algorithm, Difficulty Hard

Great score on Understanding Rate Limiting in APIs, Difficulty Medium

Great score on Ensuring Real-time Data Accuracy in Mobile App, Difficulty Medium

Take Home: Problem Solving Assessment

92%

Great score on Validate Parentheses in a String, Difficulty Medium

Great score on Word Search in Grid, Difficulty Hard

Great score on Reverse Digits of a 32-bit Integer, Difficulty Hard

Experience

Grey Invent Technologies

Software Engineer

Full-Time

Jun 2025 — Present

Led mobile development for, 91 Payments, fintech app using React Native and Expo, launched to production serving 3,000+ active users across iOS and Android

Currently leading mobile development for Kloutpay, a creator-focused fintech platform

Managed deployment pipeline for Google Play Store and Apple App Store releases

Developed frontend applications and admin panels with Next.js and Tailwind CSS, translating Figma designs into pixel-perfect production interfaces

Optimized app performance achieving 40% faster load times and 95%+ crash-free rate through efficient state management and code optimization

Collaborated with QA teams in Agile sprints to ensure quality API integrations and seamless user experience across mobile and web platforms

Technologies:

Node.js

AWS

Typescript

AWS Amplify

Next.js

React

React Native

Expo

Left Lane Technologies

Software Engineer I

Full-Time

Oct 2023 — Sep 2025

Led 5-member engineering team across frontend, backend, and cloud infrastructure, delivering 4 products in fintech, e-commerce, and SaaS with 3x faster shipping velocity

Architected and developed scalable REST and GraphQL APIs using TypeScript, Node.js, NestJS, Python, and FastAPI serving thousands of concurrent users

Developed frontend applications with Next.js and TailwindCSS, delivering responsive user interfaces and admin dashboards

Implemented comprehensive unit testing with Jest achieving 85%+ code coverage, ensuring code reliability and reducing production bugs

Integrated Stripe and Paystack payment gateways across multiple projects, implementing secure transaction processing and webhook handling

Designed and implemented microservice architecture using RabbitMQ and FastAPI for async task processing, reducing API response times by 60%

Managed AWS infrastructure (S3, SES, SNS, Lambda, API Gateway, Elastic Beanstalk, CodePipeline) ensuring 99.9% uptime and scalability

Oversaw technical communications between engineering teams and management, ensuring alignment on deliverables and sprint goals

Technologies:

TypeScript

Node.js

NestJS

Python

FastAPI

Next.js

TailwindCSS

Jest

Stripe

Paystack

RabbitMQ

GraphQL

AWS S3

AWS Lambda

AWS SES

AWS Elastic Beanstalk

Credit Cliq

Full-Time

Nov 2023 — Mar 2025

Integrated APIs with 3 major credit bureaus across US, Canada, and India, ensuring SOC2 compliance and adherence to regional security regulations

Built backend systems for mobile app serving 10,000+ users, enabling credit report access, identity verification, and credit building through bill payments

Developed credit-building features allowing users to improve credit scores via airtime purchases and electricity bill payments

Built robust REST APIs with Node.js, Hono.js, TypeScript, MongoDB, and Redis for efficient credit data processing and real-time identity verification

Implemented AWS Cognito for secure user authentication and authorization across mobile and admin applications

Integrated Stripe and Paystack payment services for automated invoice and subscription management

Developed microservice applications using Apache Kafka, and AWS Lambd for scalablitity when fetching credit reports

Established CI/CD pipelines with GitHub Actions and AWS CDK for automated deployments and infrastructure management

Technologies:

Node.js

Hono.js

TypeScript

MongoDB

Redis

AWS Cognito

Stripe

Paystack

Apache Kafka

AWS Lambda

GitHub Actions

AWS CDK

Projects

91 Payments - Currency Exchange Platform

Demo

91 Pay, is an enterprise-grade, API-first remittance and currency-exchange platform. The platform now enables businesses to move large sums of money globally with transparent, wholesale rates and developer-friendly integrations across six major fiat currencies and USDT.

Resonate - AI-Driven Sermon Discovery Platform

Demo

An AI-powered application described as the Shazam for Christian sermons. Users can discover sermon matches and explore a vast library of spiritual messages. I was responsible for the backend and AI services. I made use of Typescript, NestJS, TypeORM, Python, Fast API, LLM integrations and Vector Databases

Gaia AI - AI Powered Matching For Innovators

Demo

Gaia AI is a platform that uses AI-powered matching to connect people based on their ideas or projects. It helps users find potential co-founders, collaborators, or supporters who share similar visions for the future. It makes uses of AI to automatically create users profiles. AI powered voice onboarding is built-in, to make the onbaording process seamless and interactive

Education

BSc Computer Science

2019 - 2023

Mountain Top University

Ogun, Nigeria