You will get Performance & Scalability Optimization for JavaScript Apps
Project details
I’ll identify and fix the biggest performance bottlenecks in your JavaScript app (React/Angular/Vue + Node.js), with clear before/after metrics and practical improvements you can ship.
Programming Languages
JavaScript, TypeScriptCoding Expertise
Cross Browser & Device Compatibility, Performance Optimization, SecurityWhat's included
| Service Tiers |
Starter
$900
|
Standard
$1,400
|
Advanced
$2,000
|
|---|---|---|---|
| Delivery Time | 5 days | 7 days | 10 days |
Number of Revisions | 1 | 2 | 3 |
Design Customization | - | - | - |
Content Upload | - | - | - |
Responsive Design | - | - | - |
Source Code | - | - | - |
Frequently asked questions
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PT
Paruyr T.
Jun 1, 2026
Full-Stack SaaS Developer Needed for AI-Powered Jewelry ERP Features
Karen did an excellent job on our AI-powered Jewelry ERP features project. He quickly understood the existing SaaS architecture, product workflow, and the specific challenges around using ERP data and product images to generate reliable AI-assisted catalog content.
I would gladly work with Karen again and highly recommend him for full-stack SaaS, AI application, and ERP-related projects.
I would gladly work with Karen again and highly recommend him for full-stack SaaS, AI application, and ERP-related projects.
PT
Paruyr T.
Apr 15, 2026
Senior AI Engineer for RAG Knowledge Base + AI Marketing Content Platform
Karen did an excellent job building our AI-powered RAG knowledge base and marketing content platform. He was fast, reliable, and made strong architectural decisions throughout the project. The system he delivered was practical, well-structured, and production-ready. Communication was clear and proactive, and he consistently showed strong technical judgment with OpenAI, Pinecone, Supabase, and backend workflows. I would gladly work with him again and highly recommend him for AI and SaaS projects.
SM
Stuart M.
Jul 3, 2017
Web development: mainly Wordpress
GS
Guy S.
Jun 7, 2016
Looking for Web Development for creating Chrome Extension
GF
Glenn F.
Jan 21, 2016
Web Pages (x34) - HTML5 & AngularJS Integration (45-60 Hours - Need great design focused attention to detail!)
We provided a challenging, technical and very detail oriented role using Angular JS design. Karen performed fairly well with this project and was very responsive and capable. We were frustrated with some of the QA processes, we would definitely use him again.
About Karen
Senior Software Engineer | SaaS, AI Apps, Agents, RAG & Automation
100%
Job Success
Ottignies-Louvain-la-Neuve, Belgium - 1:46 am local time
I’m a senior software engineer with 12+ years of experience specializing in full-stack solutions . I help teams build, scale, modernize, and optimize high-performance applications with a strong focus on maintainability, reliability, and real business outcomes.
I work across JavaScript/TypeScript and Python, using React, Angular, Node.js/NestJS, FastAPI, PostgreSQL, OpenAI, RAG pipelines, and AI agent workflows.
I’ve delivered products across B2B platforms, FinTech, MedTech, CRM systems, accounting/invoicing software, SaaS dashboards, and hybrid mobile apps using technologies like React, Angular, Vue, Node.js, NestJS, React Native, Ionic, MongoDB, and PostgreSQL.
My current focus is helping businesses integrate AI-powered features into real products — including AI apps, automation workflows, RAG-based systems, AI agents, document intelligence, analytics assistants, and conversational interfaces. I use AI-assisted development where it adds speed, but all architecture, product, and production decisions stay human-driven, tested, and maintainable.
I’m strongest when the project needs more than just coding: understanding the business logic, designing the right architecture, reducing technical risk, and shipping a product that can grow after launch.
I can help with:
* SaaS MVP development
* AI-powered web applications
* RAG and document intelligence systems
* AI agents and automation workflows
* Dashboards, admin panels, and internal tools
* API integrations and third-party systems
* Codebase refactoring and performance optimization
* Hybrid mobile apps with React Native or Ionic
If you need a senior engineer who can move fast without creating a mess, I’d be happy to help turn your idea or existing codebase into a reliable product.
Steps for completing your project
After purchasing the project, send requirements so Karen can start the project.
Delivery time starts when Karen receives requirements from you.
Karen works on your project following the steps below.
Revisions may occur after the delivery date.
Audit & profiling: find the top bottlenecks
Plan: agree on the highest-impact fixes