Senior Software Engineer

Hi, I'm Eli

I build enterprise grade software and offer technical consulting to businesses looking to automate processes or integrate AI.

Vilnius, Lithuania - 🇪🇺 EU

About Me

11+Years of
Experience

120+Projects
Completed

110+Satisfied
Customers

Intro Video

90-second
intro about me

Ninety seconds to get the full picture: who I am, how I work, and exactly what I can build for you.

1:30 min

1:30

Eli Tamosauskas working on a laptop at a shared office table

About Me

What I do

I have been building enterprise-grade software and advising businesses on technology challenges for over a decade, mostly as a contractor. Occasionally I take a full-time role when the company, team, or problem fits my profile.

I do my best work in autonomous teams built on ownership, trust, and data-driven decisions. My goal is simple: solve real, ambitious problems with outcomes you can measure in numbers.

I see myself as a generalist. It lets me pick high-impact challenges I find interesting, and it means I can take an idea from concept all the way to engineering and deployment.

Outside of work, occasionally I mentor ambitious people who want to get into software engineering, write the odd blog post or take a side project.

Read my blog Read my case studies

Experience

Where I've been

Mar 2025 – Mar 2026Remote
CAST AI
Kubernetes Optimisation Platform
Senior Frontend Engineer
cast.ai
- Rewrote the app's core selector and dropdown components from scratch, restoring TypeScript type safety and redesigning a confusing, widely-disliked API into a maintainable one.
- Built the frontend for a custom AI chatbot in the dashboard, building the chat widget from scratch in collaboration with the backend team.
- Owned a legacy design system: re-architected it for API consistency across the codebase, wrote the missing documentation, and improved component composition.
ReactTypeScriptEmotionMaterial UIReact AriaGitLab CI/CDVitestRTLStorybookPlaywrightNX Monorepo
Mar 2024 – Mar 2025Hybrid
Nord Security
Digital Security & Privacy
Senior Frontend Engineer
nordsecurity.com
- Owned and shipped an internal React component library adopted across 4 product teams, giving them a consistent set of reusable components to build on.
- Drove the accessibility overhaul of the design system: evaluated options and adopted React Aria's headless components, enabling accessible primitives while keeping full control over styling.
- Introduced visual regression and integration testing into the component library and CI pipeline, catching UI regressions that the previous snapshot-based tests missed entirely.
ReactTypeScriptEmotionMaterial UIReact AriaGitLab CI/CDVitestRTLStorybookPlaywright
Jan 2020 – Aug 2023Remote contractor
Zeply
Cryptocurrency Exchange & Payments
Fullstack Engineer (frontend-focused)
- Led the effort to ship an existing React codebase to native iOS, Android and web: evaluated React Native vs. Ionic/Capacitor, presented a recommendation to the team, then implemented and shipped across all three platforms from a single codebase.
- Integrated Sumsub KYC/AML and Solidgate payments into the exchange, owning the frontend end-to-end and contributing to the backend integration in collaboration with the BE team.
- Built CI/CD pipelines from scratch for all three platforms, automating builds, testing, and deployment for iOS, Android and web.
Next.jsReactReduxEmotionNode.jsExpressPostgreSQLMongoDBTypeScriptJestVitestCypressIonicCapacitor
Jun 2017 – Jan 2020Remote contractor
Redacre
Business System Solutions
Fullstack Engineer (frontend-focused)
redacreltd.com
- Solo-designed and built a config-driven React payment app that made payment providers pluggable, supporting new SDKs and custom integrations as the business swapped providers, without app rewrites.
- Integrated third-party KYC providers and cleared a long backlog of production bugs.
Next.jsReactStyled ComponentsReduxNode.jsExpressPostgreSQLMongoDBJestCypress
Jan 2013 – May 2017Remote contractor
Webbiz
Digital Web Agency
Fullstack Web Developer
webbiz.ie
- Shipped 60+ custom projects end-to-end, translating Photoshop designs into pixel-perfect, fully customisable WordPress themes.
- Worked directly with clients from requirements through delivery and handoff.
MySQLPHPJavaScriptjQuerySCSSCSSHTML

From The Blog

My recent writing

Eli TamosauskasJul 23, 2026

691

Top 5 Lessons Learned From 2 Years Building React Design Systems

Lessons learned while architecting scalable React component design systems Honestly, I never set out to become the “go-to” design systems engineer. I come from…

design-systemsweb-developmentRead on Medium

Eli TamosauskasFeb 23, 2024

My Reputation

1 on 1 Mentorship

Eli is great at giving clear, detailed feedback on your work. He points out areas for improvement in a helpful way, making it easy to understand and apply his suggestions. He's also easy to talk to, keeping the conversation positive and encouraging, so you always feel motivated to improve.

Oleksandr ZozuliaTech Sales

B2B Contract

Eli is a solid developer with a professional attitude, problem-solving skills and a good understanding of several technologies. As a designer who worked beside him for 3 years, I affirm Eli keeps his skills up to date in order to deliver any challenge with quality & fidelity. I'm happy to recommend him for future positions.

Matheus MartinsFounder & Director @ Forkeen

B2B Contract

Eli is not only an amazing Web Developer, but also a great educator! He helped with valuable insights in the improvement of our Web Development program and prepared high-quality material, explaining complex topics in a very easy-to-understand way. Combining high technical expertise and great soft skills needed by top mentors is a rare combination, but Eli is definitely someone who does this masterfully!

Giedrius ŽebrauskasChief Academic Officer, Turing College

1 on 1 Mentorship

It was a pleasure to study under Eli's mentorship. Starting in a new industry can be intimidating. Still, Eli not only helped with his knowledge and industry insights but, most importantly, motivated and inspired me to move forward, improve, and try different approaches when something wasn't working. His guidance went beyond technical skills, encompassing professional development and personal growth.

Martynas GrumadasBackend Engineer

B2B Contract

Eli has a hunger to learn which he daily applies at his place of work. When faced with a problem, he does not accept to stop at the surface. Rather, Eli digs deeper to understand what is the root cause and come up with a sustainable solution. Eli never stands back to share his opinion and he always seeks to push everyone to the next level.

Andrea MangionQA Lead at Betsson Group

Engineering

It's a pleasure to work with Eli, he's always open to help and step up for the tasks that no one else dares to do. He's always active in the discussions and he's not afraid to point out his opinion even if it's opposite of the team's decision. He's so innovative and he always looks for better and newer solutions for problems.

Vahid KaramiSenior Full-Stack Developer

Tooling

My tech stack

Most of my projects are built using the modern TypeScript ecosystem. On frontend single page applications I stick with React and TanStack. If the project needs SEO or server side rendering I reach for Next JS. For testing I like Playwright, RTL and Vitest.

For building backend REST API's I go with Node & Express paired with PostgreSQL. Supabase is often a good all rounder choice too.

Figma for design, mockups etc.

React

TypeScript

NextJS

NodeJS

PostgreSQL

Vite

Claude Code

Supabase

Storybook

Tailwind

RTL

ZOD

Playwright

Figma

TanStack

Recent Projects

My recent work

NSNord Supply Co.

Design System Creation

Built a full component library and design tokens from scratch, then migrated the storefront onto it. Shipping features now takes days, not weeks.

Read full case study

ReactTypeScriptNext.js

FBFluent Billing

Payments Platform

Designed and shipped a Stripe-backed subscription engine with metered billing, dunning and a self-serve customer portal.

Read full case study

Next.jsNode.jsPostgreSQL

CCobalt

Systems Architecture

Untangled a legacy monolith into well-bounded services, cutting deploy times in half and stabilising a platform three teams depend on.

Read full case study

DockerRedisNode.js

See full archive of my work

What I Offer

My services

Download CV

Hire me

B2B Contracting

Looking for an experienced senior software engineer to join your project? Hire me as a B2B contractor. I handle my own legal incorporation, invoicing and taxes.

Ideal forHR looking for a flexible B2B contractor.

Full-Time Opportunities

I occasionaly consider full-time roles where I can make a meaningful impact. If you think I would be a good fit for your project - reach out.

Ideal forHR hiring for a permanent technical position.

Other Services

1 on 1 Mentorship

Looking to launch your engineering career to a new level? I offer high intensity 1 on 1 mentorship sessions. We will review your current technical knowledge and set concrete, measurable learning goals. We build skills trough hands on projects and 1 on 1 code reviews.

Ideal forAspiring engineers looking to grow their skills with structured, one-on-one support.

Business Process Automation & Consulting

Want to leverage AI and automation in your business? Turn repetitive, manual work into reliable automated workflows, connecting tools you already use and/or implementing new ones. I audit your business processes end-to-end and propose automation solutions.

Ideal forBusiness owners looking for technical help.

Still Looking?

Contact me

If nothing above fits neatly, that's fine. Most good projects don't. Tell me what you're trying to build and I'll help you figure out the right approach.

The Bookshelf

Books I recommend

The ones that shaped how I build software and carry myself as a professional, with the occasional detour into life.

The Clean Coder

Robert C. Martin

★★★★★5.0 / 5

A time tested & classic guide to conducting yourself as a professional in the industry.

My take

I keep coming back to this one from time to time. I believe it's an essential pre-requisite to every engineer on how a professional craftsman should work and deal with colleagues.

View on Goodreads

Eloquent JavaScript

Marijn Haverbeke

★★★★★5.0 / 5

Introduction to Javascript from beginner to expert level.

My take

This is a book I've used to study javascript in the early days of my career. I am a strong believer in learning trough practice. I keep recommending this one to my mentees because I believe this book has a good balance between theory and hands on practice.

View on Goodreads

The Pragmatic Programmer

David Thomas & Andrew Hunt

★★★★★5.0 / 5

A career book about the habits and mindset of an effective developer, rather than any specific language or technology.

My take

If I was to recommend you only one book it would be this. I find myself refering back to it on a regular basis when I'm not satisfied with my decisions or performance.

View on Goodreads

Total TypeScript

Matt Pocock

★★★★★5.0 / 5

If you're an experienced JavaScript developer or want to level up your current TypeScript skills, with Total TypeScript, you'll learn everything you need to build a TypeScript product from scratch.

My take

In my opinion, Matt Pocock creates the best TypeScript education content. Anyone looking to get serious about TypeScript will find answers here.

View on Goodreads

What I do

I do my best work in autonomous teams built on ownership, trust, and data-driven decisions. My goal is simple: solve real, ambitious problems with outcomes you can measure in numbers.

I see myself as a generalist. It lets me pick high-impact challenges I find interesting, and it means I can take an idea from concept all the way to engineering and deployment.

Outside of work, occasionally I mentor ambitious people who want to get into software engineering, write the odd blog post or take a side project.

My tech stack

Hi, I'm Eli

90-secondintro about me

What I do

Where I've been

CAST AI

Nord Security

Zeply

Redacre

Webbiz

My recent writing

Top 5 Lessons Learned From 2 Years Building React Design Systems

TOP 3 Problems with Programming Courses Sold in Lithuania

My Reputation

My tech stack

My recent work