Sean Amarasinghe

About

Hi, I'm Sean — a Lead Engineer with over two decades of experience across the full frontend and full-stack spectrum. I specialise in JavaScript/TypeScript, React, Vue.js, Golang, and Python, and I've spent recent years focused on integrating Generative AI and LLM-powered features (recommendation engines, RAG, agentic systems) into large-scale production web platforms.

I've led engineering teams, driven monorepo and CI/CD modernization efforts, and partnered closely with product, data science, and design teams to ship AI-driven features responsibly and at scale.

Education

Books & Courses

Projects

TWE — Travel World & Explore
A travel discovery guide featuring curated European city profiles — from Bergen to Vienna — alongside in-depth destination articles and itineraries.
Read case study
Segrep
A developer security platform that bundles six core vulnerability scanners (Trivy, Semgrep, Gitleaks, Checkov, Syft, and OSV/GHSA dependency scanning) into a single Docker image — with SARIF export, policy-as-code, and CI gating.
Read case study
MyMovieDB
A personal movie catalogue for tracking watched films with their related actors and genres, featuring popularity rankings and ratings.
Read case study
RetroCric
A digital magazine celebrating cricket's golden years — the stories, rivalries, and iconic moments that shaped the game, with feature articles and a learn section.
Read case study

Experience

Nov 2025 — Present
Senior Software Engineer · EntainRemote
Vue 3 Composition API + TypeScript monorepo powering the AI-driven Casino vertical across a multi-brand web platform.
- Built the casino lobby, game discovery, launch, and in-game player experiences (Vue 3, TypeScript, Tailwind, Golang gRPC microservices).
- Integrated GraphQL game / promotions / rewards / player-profile services with Vue Query and Pinia.
- Built agentic LLM systems: planning, tool use, and memory orchestration (LangGraph, Pydantic).
- Delivered AI-powered game recommendations and personalized promotions/rewards via ML segmentation.
- Established experimentation / A/B testing frameworks and Vitest coverage within an npm-workspaces monorepo.
Aug 2021 — Oct 2025
Lead Engineer · SeekMelbourne
Led a team of 5 engineers across Brand Experience & Job Posting (company profiles and job posting).
Engineers led
5
Faster builds
20%
More code reuse
20%
Faster CI
30%
- Consolidated repositories into Nx/PNPM monorepos, delivering 20% faster builds and 20% more code reuse.
- Optimized Buildkite CI/CD with artefact caching and dependency-graph analysis for 30% faster builds.
- Architected the Company Profiles platform (Next.js App Router, React, TypeScript, Node.js, AWS).
- Shipped production GenAI: job-ad creation and content enrichment/moderation via Amazon Bedrock.
- Built real-time AI streaming (SSE), RAG integration, and prompt orchestration & governance frameworks.
- Re-engineered Playwright E2E suites with AI-assisted test generation.
Jan 2019 — Aug 2021
Principal Engineer (Frontend) · Cricket AustraliaMelbourne
Principal Engineer (Oct 2019 – Aug 2021) and previously Lead Frontend Developer (Jan 2019 – Oct 2019) on cricket.com.au and playcricket.com.au.
Engineers mentored
3
- cricket.com.au – The digital website for Cricket Australia. playcricket.com.au – Grassroots cricket platform.
- Provided the frontend engineering team with best practices and technical guidance.
- UI stack contained Next.js, React, Flow, styled-components and Apollo/GraphQL. Source control with Git/GitHub.
- End-to-end testing with Cypress and unit testing with Jest. Static analysis tools including ESLint and SonarCloud.
- .NET/Azure platform for API.
Jan 2018 — Jan 2019
Software Engineer · InterNationsMunich
Software engineer on the InterNations web application, working with a small Agile team.
- InterNations web application – The desktop application for InterNations. Worked with a small team of Agile developers.
- UI stack contained React/Redux, Flow, Sagas and styled-components, plus Backbone. Source control with Git.
May 2016 — Jan 2018
Senior Front End Developer · RXP ServicesMelbourne
Senior front end developer on Telstra Health and Sendle eBay Integration, working with a mid-sized Agile team.
- Telstra Health – Bespoke solution to help healthcare organisations improve patient comfort, provide home healthcare services, automate monitoring, and streamline routine tasks.
- Sendle – eBay Integration – Integrating with the eBay third-party API. Worked with a mid-sized team of Agile developers.
- UI stack contained React/Redux, Sagas and LESS. Unit testing with Jest. Tools including ESLint, StyleLint and Webpack.
- .NET Microservices and backend; some projects involving a Ruby on Rails backend.

Leadership

People leadership
I lead engineering teams with a focus on clarity, mentoring, and shipping responsibly at scale — partnering closely with product, design, and data science.
- Led a team of 5 engineers at Seek across Brand Experience and Job Posting.
- As Principal Engineer at Cricket Australia, led and mentored a team of 3 frontend engineers.
- Drove monorepo and CI/CD modernization that improved build speed and code reuse.
- Guided teams shipping production GenAI features with strong engineering and governance practices.
Cross-team / organisational influence
I set technical direction across product lines and partner teams — from monorepo and CI/CD standards to GenAI governance — often without owning every team involved.
- At Seek, consolidated Brand Experience and Job Posting repositories into Nx/PNPM monorepos and reshaped Buildkite CI/CD (caching, dependency-graph analysis), aligning multiple squads on shared tooling and cutting builds by ~20–30%.
- Architected Company Profiles (Next.js, React, TypeScript, Node.js, AWS) and partnered with product, data science, and platform teams to ship production GenAI — job-ad creation, Bedrock enrichment/moderation, SSE streaming, RAG, and prompt governance.
- As Principal Engineer at Cricket Australia, set frontend standards and technical guidance across cricket.com.au and playcricket.com.au while coordinating with .NET/Azure API teams on integration and quality (Cypress, Jest, SonarCloud).
- At Entain, delivered Casino experiences across a multi-brand platform — GraphQL player/promotions services, experimentation frameworks, and agentic LLM systems — coordinating frontend, Golang microservices, and ML segmentation partners.
Mentorship and multiplying others
I grow engineers and raise the org's technical bar — through mentoring, design reviews, shared standards, and better tooling — so the team's output compounds beyond my own.
- At Seek and Cricket Australia, mentored junior and mid-level engineers day-to-day — pairing on delivery, running design reviews, and coaching career growth across teams of 5 and 3 respectively.
- Raised the technical bar with shared practices: Nx/PNPM monorepo conventions and Buildkite improvements at Seek; ESLint/SonarCloud quality gates, Cypress E2E, and Jest standards at Cricket Australia.
- Improved how teams ship — re-engineered Playwright suites with AI-assisted test generation at Seek, and established Vitest coverage and experimentation frameworks in Entain's Casino monorepo.
- Multiplied impact beyond the team through teaching: author of Service Worker Development and a Newline course on enterprise monorepos with Nx and PNPM.
Ambiguity and judgment
I take vague, open-ended problems and turn them into the right technical and product path — especially in 0-to-1 systems, migrations, and production AI where requirements start fuzzy and the stakes are high.
- At Seek, framed Company Profiles from an open product brief into a concrete Next.js/AWS architecture, then shipped production GenAI (job-ad creation, Bedrock enrichment/moderation, RAG, SSE) with prompt orchestration and governance so teams could move without guessing the guardrails.
- Led the Brand Experience & Job Posting monorepo and Buildkite CI/CD migration — a high-ambiguity platform change across multiple squads — defining the target state, sequencing the cutover, and delivering ~20–30% faster builds with clearer ownership.
- At Entain, shaped 0-to-1 Casino experiences and agentic LLM systems (LangGraph planning, tool use, memory) where player journeys and AI behaviour were still being defined, pairing experimentation frameworks with careful GraphQL/gRPC service boundaries.
- As Principal Engineer at Cricket Australia, guided cricket.com.au and playcricket.com.au through evolving frontend standards and .NET/Azure integrations when product and platform requirements shifted across two major digital surfaces.
- Demonstrated judgment on pace: move fast behind A/B and Vitest safety nets (Entain Casino; Seek Playwright AI-assisted rework), and slow down for irreversible risks — GenAI content moderation, prompt governance, and monorepo/CI cutovers that affect every squad.
Communication artifacts
I write and present the artifacts that align engineers and stakeholders — design docs, RFCs, postmortems, and technical writing — and translate fluidly between technical depth and business outcomes.
- At Seek, authored design docs and RFCs for Company Profiles architecture and the Nx/PNPM monorepo + Buildkite CI/CD migration, so multiple squads shared a clear target state, sequencing, and ownership model before cutover.
- Defined GenAI prompt orchestration and governance frameworks for production Bedrock features (job-ad creation, enrichment/moderation, RAG, SSE) — turning model behaviour, risk, and product goals into written standards teams could execute against.
- As Lead Engineer and Principal Engineer, regularly presented technical options and trade-offs to product, data science, and leadership stakeholders — from Brand Experience/Job Posting roadmaps at Seek to frontend standards across cricket.com.au and playcricket.com.au.
- Translate between technical and business language: framing Casino recommendations and promotions for multi-brand player outcomes at Entain, and GenAI job-ad tooling in terms of recruiter productivity and marketplace quality at Seek.
- Publish durable technical communication beyond the day job — Service Worker Development, a Newline course on enterprise monorepos with Nx and PNPM, and ongoing blog and Medium writing that teaches patterns others can reuse.

Skills

Languages

Programming languages used across frontend, backend, and data layers.

Frameworks

Building scalable frontend and full-stack applications across the JavaScript ecosystem.

Databases

Designing and working with relational data stores for production applications.

Cloud

Designing and shipping applications on modern cloud platforms.

Infrastructure

Containerising and orchestrating workloads for reliable, scalable delivery.

AI / ML

Integrating Generative AI and LLM-powered features into large-scale production platforms.

Writing

Featured

Latest on Medium

Read on Medium Browse all posts on my blog (old)

Contact

Let's build something.

I'm always happy to talk about engineering leadership, AI-powered product work, or an interesting problem worth solving. Whether you have a role in mind or just want to connect, my inbox is open.

Lead Engineer

About

Education

Books & Courses

Projects

TWE — Travel World & Explore

Segrep

MyMovieDB

RetroCric

Experience

Senior Software Engineer · EntainRemote

Lead Engineer · SeekMelbourne

Principal Engineer (Frontend) · Cricket AustraliaMelbourne

Software Engineer · InterNationsMunich

Senior Front End Developer · RXP ServicesMelbourne

Leadership

People leadership

Cross-team / organisational influence

Mentorship and multiplying others

Ambiguity and judgment

Communication artifacts

Skills

Languages

Frameworks

Databases

Cloud

Infrastructure

AI / ML

Writing

Improve JavaScript Performance with Tree Shaking

Improving Next.js Performance

Server Side Rendering with Suspense in React 18

NextJS Client-side, Server-side & Static Rendering

SERVICE WORKERS

What are daemon threads?

Stop Writing Terraform Like It’s a Script: Build It Like a Software Project

What are Embeddings in AI? And why you should know it

Contact

Let's build something.