Sean Jaeger

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.

Available for opportunities
🏆 Top 3% LeetCode • 🚀 £4M+ Funding Raised

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

JavaScript & TypeScriptStrong

ES6+, Modern JS patterns

React.js / Next.jsStrong

Hooks, Context, Redux, SSR

React NativeStrong

Cross-platform mobile apps

HTML5 & CSS3Strong

Semantic markup, Flexbox, Grid

Tailwind CSSStrong

Utility-first styling

Backend Development

PythonStrong

Django, FastAPI, Data Analysis

GoCompetent

Concurrent programming, APIs

Node.jsCompetent

Express, REST APIs

Django / DRFCompetent

Full-stack web applications

PostgreSQLCompetent

Database design, optimization

Cloud & DevOps

AWSStrong

EC2, S3, Lambda, RDS

CI/CDStrong

GitHub Actions, automated deployment

DockerCompetent

Containerization, Docker Compose

UbuntuCompetent

Server administration

ServerlessCompetent

Lambda functions, API Gateway

Mobile Development

React NativeStrong

iOS & Android apps

ExpoStrong

Rapid prototyping, deployment

Mobile UI/UXCompetent

Platform-specific design

App Store DeploymentCompetent

iOS & Android stores

Design & Tools

FigmaStrong

UI/UX design, prototyping

Responsive DesignStrong

Mobile-first approach

User ExperienceCompetent

User research, testing

Design SystemsCompetent

Component libraries

Algorithms & CS

Data StructuresStrong

Arrays, Trees, Graphs, Hash Tables

AlgorithmsStrong

Sorting, Searching, Dynamic Programming

System DesignStrong

Scalable architecture patterns

LeetCodeStrong

Top 3% globally ranked

Competitive ProgrammingStrong

Top 0.8% in 20K+ competition

Notable Achievements

Top 3%
LeetCode Global Ranking
£4M
Raised Across StartUps
5+ Years
Startup Experience

Professional Experience

5+ years building products and scaling teams at early-stage startups

Software Engineer

Recirculate Systems

August 2023 – Present
Full-time
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
GoNext.jsTailwindWebSocketsAWSCI/CD

Software Engineer

Ancoris

September 2022 – April 2023
Full-time
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
ReactTypeScriptNode.jsIoTTesting

React Native Developer

Kimo

June 2021 – September 2021 (4 month contract)
Contract
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
React NativeExpoTypeScriptFirebaseAnalytics

Frontend Developer

DataZoo

December 2020 – May 2021 (6 month contract)
Contract
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
ReactFigmaJupyterLabPlotlyPandasPython

Founding Software Engineer

Human Lambdas

November 2019 – November 2020
Founding Team
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
TypeScriptReactDjangoPythonNode.js

My Work

Featured
Eloquent Screenshot - Click to visit project
View Live Project

Eloquent

Live
React NativeTypeScriptExpoLLaMA 3React ReanimatedGesture Handler

Eloquent is an innovative language learning platform that combines spaced repetition with AI-powered definitions, delivering a seamless mobile experience across iOS and Android.

4 months
Timeline
AI-powered learning
Impact
Featured
Recirculate Systems Screenshot - Click to visit project
View Live Project

Recirculate Systems

Live
ReactNext.jsPythonGoPostgreSQLRFID Integration

Recirculate Systems revolutionized sustainable consumption through an innovative reusable cup system that eliminated single-use waste while maintaining convenience for both businesses and consumers.

2+ years
Timeline
Zero waste solution
Impact
Human Lambdas Screenshot - Click to visit project
View Repo

Human Lambdas

Completed
TypeScriptReactDjangoPythonUI/UX Design

Human 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.

Seedcamp backed
Funding
One year
Timeline
Competitive Programming Screenshot - Click to visit project
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Competitive Programming

Completed
PythonAlgorithmsData StructuresProblem Solving

During my focused study of Computer Science fundamentals, I immersed myself in competitive programming, tackling complex algorithmic challenges under time constraints.

12 months
Timeline
Top 3% globally
Impact

Key Achievements & Impact

Quantifiable results from 5+ years of building impactful software solutions

Top 3%

LeetCode Ranking

Global ranking among millions of developers

Top .8%

Competition Performance

Ranked top 160 of 20,000+ participants in competitive programming

£4M+

Funding Secured

Direct contribution to startup funding rounds

120K+

User Impact

Early adopters gained through product development

62% → 81%

Test Coverage

Improved enterprise platform test coverage

10,000+

IoT Fleet Scale

Devices managed in real-time monitoring platform

10,000+

Concurrent Connections

Engineered high-performance real-time systems proven at scale

6 weeks

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

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