Senior Full-Stack Software Engineer

Shay Rosner builds reliable web products across frontend, backend, and product ambiguity.

I specialize in React, Next.js, TypeScript, API design, performance, and security-sensitive systems. My best work happens where teams need someone who can clarify the problem, own the implementation, and explain the tradeoffs clearly.

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Ambiguity to execution

I turn open-ended product and system problems into scoped plans, clear tradeoffs, and shipped software.

Performance and reliability

I improve load paths, test confidence, data flow correctness, and operational visibility where user trust matters.

Secure full-stack delivery

I build across React, Next.js, TypeScript, Node.js, APIs, auth, payments, and sensitive data workflows.

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Selected Work

Featured Projects

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50+ Features shipped25% Engagement lift

CrowdCoursing Platform

Full-stack feature delivery across education workflows

Owned production features across admin, instructor, and student workflows with strong client/server boundaries and repeatable implementation patterns.

ReactTypeScriptGraphQLOpenAPIC#

AI chat Core productSecure sessions Auth model

Chelle.ai Chat Platform

Real-time AI chat with secure session boundaries

Designed and delivered a real-time AI chat product with onboarding, authentication, encrypted data handling, and production operations.

Next.jsReactClerkFirebaseDocker

Technical Writing

Recent Articles

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From 10.1s to 4.5s: A Frontend Performance Turnaround

10.1s -> 4.5s speed index

March 2026 · 8 min read

Summary: A practical playbook for profiling bottlenecks, removing fetch waterfalls, and improving perceived speed without backend changes.

Topics: Performance, React, Next.js, Web Vitals

Designing a Reliable AI Document Ingest Pipeline

50k+ docs, <200ms retrieval

March 2026 · 10 min read

Summary: How to structure ingestion, chunking, vector storage, and operational safeguards for large mixed-format document sets.

Topics: AI, RAG, Supabase, pgvector, TypeScript

Money-Safe Logic in JavaScript Systems

Launch-ready for 10k+ users

April 2026 · 7 min read

Summary: Lessons from fixing financial correctness under deadline pressure: data representation, rounding safety, and regression guards.

Topics: Backend, Node.js, Testing, Financial Systems

Experience

Experience Snapshot

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Senior Software Engineer

CrowdCoursing

October 2023 - Present

Built and shipped .NET backend features in C# with clean layering, automated tests, and tightened edge-case behavior.
Owned and delivered 50+ full-stack features across React, TypeScript, and GraphQL for admin, instructor, and student workflows.
Owned an end-to-end resume upload flow with strict client-side validation to protect user-entered data and backend services.

Software Engineer

ByteBot

May 2024 - Present

Reduced page load latency by 55% by removing request waterfalls and parallelizing independent fetches.
Refactored Node.js and MongoDB money flows ahead of a 10k+ user launch to prevent rounding drift.
Strengthened platform quality with robust Jest tests reaching 98% coverage.

Software Engineer

Chelle.ai

November 2023 - February 2024

Designed and delivered a real-time AI chat platform with encrypted data and secure session handling.
Built onboarding and authentication flows with Next.js, Clerk, and Firebase.
Implemented server-side session handling and API boundaries for user context, secrets, and message history.

Core Technical Skills

TypeScriptJavaScriptReactNext.jsNode.jsC#.NETGraphQLPostgreSQLMongoDBFirebaseAWSDockerJestCypressWCAG 2.x