Sean Jaeger
Software Engineer • 5 Years Experience • Startup Specialist
Proven track record building products that secure funding and scale to thousands of users. Specializing in early-stage startups with expertise in full-stack development, system architecture, and team leadership.
About Me
Hi, I'm Sean 👋
I'm a software engineer who thrives in the chaos of early-stage startups. Over the past five years, I've helped build products that secured millions in funding and scaled to thousands of users.
My superpower? Turning ambitious ideas into working products, fast. At Kimo, I built an MVP in 6 weeks that directly secured €3M in funding and attracted 120,000 early adopters. When our senior engineer left, I stepped up as de facto CTO, architecting the v2 platform that became the cornerstone of their Series A pitch.
Currently, I'm at Recirculate Systems, where I've built a real-time tracking system handling 10,000+ concurrent connections using Go and WebSockets. Before this, I scaled Rentokil's IoT platform managing 20,000+ devices across the UK, boosting test coverage from 62% to 81% along the way.
What drives me is the intersection of technical excellence and real-world impact. I've ranked in the top 4% on LeetCode and placed in the top 0.8% in competitive programming competitions. But I'm equally passionate about the human side - mentoring teams, running sprints as scrum master, and translating complex technical decisions for investors and stakeholders.
My journey started unconventionally. At 18, while finishing A-levels, I taught myself JavaScript and joined Human Lambdas as a founding engineer. That experience of building from zero taught me that resourcefulness beats resources every time.
Beyond the terminal, you'll find me training as a Judo black belt, exploring new countries as a digital nomad, or improving my Spanish. I believe diverse experiences make better engineers - whether it's the discipline from martial arts or the adaptability from constant travel.
I'm drawn to ambitious teams solving hard problems. If you're building something that matters and need someone who can ship fast without sacrificing quality, let's talk.
Technical Skills
A comprehensive overview of my technical expertise and proficiency levels
Frontend Development
ES6+, Modern JS patterns
Hooks, Context, Redux, SSR
Cross-platform mobile apps
Semantic markup, Flexbox, Grid
Utility-first styling
Backend Development
Django, FastAPI, Data Analysis
Concurrent programming, APIs
Express, REST APIs
Full-stack web applications
Database design, optimization
Cloud & DevOps
EC2, S3, Lambda, RDS
GitHub Actions, automated deployment
Containerization, Docker Compose
Server administration
Lambda functions, API Gateway
Mobile Development
iOS & Android apps
Rapid prototyping, deployment
Platform-specific design
iOS & Android stores
Design & Tools
UI/UX design, prototyping
Mobile-first approach
User research, testing
Component libraries
Algorithms & CS
Arrays, Trees, Graphs, Hash Tables
Sorting, Searching, Dynamic Programming
Scalable architecture patterns
Top 3% globally ranked
Top 0.8% in 20K+ competition
Notable Achievements
Professional Experience
5+ years building products and scaling teams at early-stage startups
Software Engineer
Recirculate Systems
Key Responsibilities
- Built and onboarded customers to MVP showcased to investors that secured £1.4M in investment
- Built real-time application using Go, Next.js, Tailwind, and WebSockets for instant payment provider engagement. Stress tested with 10K+ concurrent connections
- Built comprehensive CI/CD pipelines for all projects with automated testing and deployment
- Managed all AWS deployments and infrastructure
- Integrated payment providers for secure transactions
- Set up logging systems with automated log rotation
- Supervised sprints as scrum master
Key Achievements
- Secured £1.4M investment through MVP demonstration
- Delivered scalable real-time infrastructure handling 10K+ concurrent users
- Ensured operational reliability via automated pipelines and monitoring
Technologies Used
Software Engineer
Ancoris
Key Responsibilities
- Maintained and scaled a React platform managing Rentokil's entire UK IoT device fleet (20,000+ pest control units), enabling real-time monitoring for 1000+ field technicians
- Resolved production bugs and partnered with QA team to establish regression testing practices, improving overall platform stability
Key Achievements
- Increased test coverage from 62% to 81%, achieving 90%+ on critical paths
- Established scalability patterns that supported growth in device fleet during my tenure
- Stabilised platform through regression testing and QA collaboration
Technologies Used
React Native Developer
Kimo
Key Responsibilities
- Built Expo React Native MVP that directly secured €3M funding round, gaining 120K+ early adopters
- Stepped up as de facto CTO after senior departure, architecting v2 transformation based on user data and stakeholder interviews
Key Achievements
- Delivered investor demo prototype in 6-week sprint that became cornerstone of successful Series A pitch deck
- Analyzed user behavior metrics and conducted customer interviews, pivoting features that increased retention
- Mentored team of 3 engineers while maintaining aggressive delivery timeline for funding milestones
- Partnered directly with founder on technical due diligence and presenting architecture decisions to VCs during funding
Technologies Used
Frontend Developer
DataZoo
Key Responsibilities
- Created DataZoo's data analysis UI with Figma, continuously collaborating with the CEO and CTO
- Implemented various JupyterLab-based UI views, tailored for timeseries data analysis
Key Achievements
- Sanitized & prepared Plotly and Pandas DataFrames to generate dynamic, interactive graph views for in-depth big data analysis
Technologies Used
Founding Software Engineer
Human Lambdas
Key Responsibilities
- Joined as a founding engineer at Seedcamp-backed startup
- Collaborated with a team of developers to develop the TypeScript React web app for the company's distributed data labeling platform
- Created multiple endpoints for the Django backend including designing the database models
- Engaged in code reviews, working closely with the product manager and senior team members
- Refactored critical portions of the codebase during product iterations, including a complete overhaul of the front end
Key Achievements
- Took part in company-wide discussions covering product design, implementation, and overall company strategy
- Received regular mentorship in software engineering and UI/UX best practices from the three other team members
- Helped shape core architecture from the ground up as founding engineer
Technologies Used
My Work
Eloquent
LiveEloquent is an innovative language learning platform that combines spaced repetition with AI-powered definitions, delivering a seamless mobile experience across iOS and Android.
The app leverages locally-run LLaMA 3 to generate comprehensive and contextual definitions, ensuring reliable access to high-quality learning materials without dependency on external APIs.
Built with React Native and Expo, the application emphasizes performance and user experience through fluid animations and gesture-based interactions.
Recirculate Systems
LiveRecirculate Systems revolutionized sustainable consumption through an innovative reusable cup system that eliminated single-use waste while maintaining convenience for both businesses and consumers.
As a key member of the engineering team, I developed full-stack solutions spanning from user-facing applications to complex backend systems handling real-time RFID tracking and payment processing.
The platform integrated seamlessly with existing point-of-sale systems, making adoption frictionless for partner cafes while ensuring accurate tracking and billing.
Human Lambdas
CompletedHuman Lambdas, backed by Seedcamp, pioneered Human-in-the-Loop infrastructure for reliable and scalable data labeling, enabling high-quality training data generation for machine learning systems.
As a founding engineer joining at 18, I played a crucial role in building both the TypeScript React frontend and Django backend, establishing core functionality and scalable architecture.
Working in a tight-knit team of four, I contributed across the full stack while participating in strategic decisions that shaped the product and company direction.
Competitive Programming
CompletedDuring my focused study of Computer Science fundamentals, I immersed myself in competitive programming, tackling complex algorithmic challenges under time constraints.
Through consistent practice and deep understanding of data structures and algorithms, I achieved great success in global competitions, demonstrating both technical proficiency and problem-solving abilities.
This intensive period of study and practice markedly enhanced my ability to architect efficient solutions and quickly master new technologies.
Key Achievements & Impact
Quantifiable results from 5+ years of building impactful software solutions
LeetCode Ranking
Global ranking among millions of developers
Competition Performance
Ranked top 160 of 20,000+ participants in competitive programming
Funding Secured
Direct contribution to startup funding rounds
User Impact
Early adopters gained through product development
Test Coverage
Improved enterprise platform test coverage
IoT Fleet Scale
Devices managed in real-time monitoring platform
Concurrent Connections
Engineered high-performance real-time systems proven at scale
Sprint Performance
Investor demo prototype delivery timeline
What Sets Me Apart
Founding Team Member
Multiple early-stage startups from idea to funding
Product Growth Expert
Consistently delivered products that scale and secure investment
Technical Excellence
Self-taught Computer Science with focus on algorithms and system design
Ready to make an impact together?
Let's discuss how my experience can contribute to your team's success