Publication
JavaScript Best Practices and Tips by Toptal Developers
https://www.toptal.com/developers/javascript/tips-and-practices
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John Ginsberg
Verified Expert in Engineering
Full-stack Developer
Southend-on-Sea, United Kingdom
Toptal member since December 10, 2013
Bio
With over 30 years of experience in software development and two decades in engineering leadership, John has spent his career transforming complex technology into real-world products that scale. Today, he helps companies leverage the new frontier in product development: language models and autonomous AI agents. John collaborates with ambitious teams to design and build AI-powered products that are not only technically sound but also commercially viable, user-focused, and scalable.
Portfolio
Intuit
Agentic AI, Claude Agent SDK, QuickBooks API
LangCraft
Agentic AI, Agentic Frameworks, LangChain, Model Context Protocol (MCP)...
Klarna
Team Leadership, System Architecture, Amazon Web Services (AWS)...
Experience
- Chrome Extensions - 9 years
- Zendesk API - 3 years
- AWS HA - 2 years
- LangChain - 2 years
- Generative Artificial Intelligence (GenAI) - 2 years
- AWS Lambda - 2 years
- AI Agents - 1 year
Preferred Environment
MacOS, Slack, GitHub
The most amazing...
...thing I've built is a real-time interactive analytics dashboard that updated its display every few seconds.
Work Experience
Principal AI Engineer
2025 - PRESENT
Intuit
- Built various agentic AI integrations with QuickBooks.
- Expanded QuickBooks AI initiatives to international markets.
- Created agentic AI tools to improve customer experiences.
Technologies: Agentic AI, Claude Agent SDK, QuickBooks API
Founder
2025 - PRESENT
LangCraft
- Built a multi-agentic customer support and product search chatbot.
- Automated content production using large language models (LLMs) and supported by dynamic web search.
- Built a ChatGPT app and MCP interface, with back-end API support.
Technologies: Agentic AI, Agentic Frameworks, LangChain, Model Context Protocol (MCP), OpenTelemetry, ChatGPT, Claude, QuickBooks API
Domain Architect | Senior Engineering Manager
2021 - 2024
Klarna
- Assisted with the launch of numerous client-side (app and web) product experiences.
- Helped to establish architectural standards that further aligned the app, web, and browser extension products.
- Oversaw re-architecture of the browser extension as a platform to which dozens of feature teams now contribute.
Technologies: Team Leadership, System Architecture, Amazon Web Services (AWS), Technical Leadership, Domain-driven Development, Enterprise Architecture, Web Marketing, React, TypeScript, Artificial Intelligence (AI), Next.js, Full-stack, REST APIs, Generative Artificial Intelligence (GenAI), LangChain, Retrieval-augmented Generation (RAG), Architecture, Chrome Extensions, API Integration, AI Agents
CTO
2014 - 2021
Piggy (sold to Klarna)
- Designed and architected the full technology stack.
- Built a Chrome browser extension that is actively used by more than 1 million users.
- Implemented and maintained a back-end infrastructure with 99.99% uptime.
- Created an affiliate tracking, reporting, and payment solution.
- Assisted with the evaluation and recruitment of team members.
Technologies: Amazon Web Services (AWS), Vagrant, Redis, React, DevOps, JavaScript, PHP, Technical Leadership, Software Architecture, Cloud Architecture, CTO, Software Development, Enterprise Architecture, Team Leadership, Next.js, Tailwind CSS, Full-stack, REST APIs, Architecture, Chrome Extensions, API Integration, APIs
Developer
2017 - 2017
DSI
- Built a simple Ionic app that integrates with Zendesk, across both iOS and Android platforms.
- Customized Cordova plugins.
- Enabled push notifications and built a simple web-based UI for sending.
Technologies: Ionic 3, Software Architecture, Software Development, Full-stack, REST APIs, API Integration
Developer
2017 - 2017
Silverback IS
- Built an Ionic application for Android.
- Integrated with various hardware devices via custom Cordova plugins.
- Wrote to remote PouchDB server via local CouchDB library.
Technologies: CouchDB, Ionic, Software Architecture, Software Development, Full-stack, REST APIs, API Integration
Developer
2016 - 2017
Pacific Islands Forum Fisheries Agency
- Built a hybrid iOS and Android application using Ionic 2 and subsequently Ionic 3.
- Enabled offline use and automated online sync of data when connected.
- Synchronized with various third-party and custom APIs.
Technologies: CouchDB, Ionic 3, Ionic 2, Software Architecture, Software Development, Full-stack, REST APIs, API Integration
Lead Developer
2014 - 2014
SynMedia
- Implemented a mobile app development framework based on Ionic and AngularJS.
- Created a mobile app builder and CMS.
- Integrated with third-party services like PhoneGap Build, Google Maps, and Pushwoosh.
- Deployed apps via Testflight.
- Designed an app experience that can be changed in real time via SaaS-based CMS.
Technologies: MySQL, JSON, PHP, JavaScript, Google Maps, Pushwoosh, PhoneGap, Ionic, AngularJS, Software Architecture, Software Development, Full-stack, REST APIs, API Integration
PHP Developer
2013 - 2014
Zendesk (via Toptal)
- Created a PHP wrapper library around the existing REST APi.
- Wrote a test suite for each endpoint.
- Implemented the PSR-0 standard.
- Integrated with and implemented a composer package.
- Implemented OAuth2 authentication.
Technologies: PHP 5, Software Development, Full-stack, REST APIs, API Integration
Product Director
2000 - 2013
Ensight
- Built an email and SMS delivery engine employing parallel processing and job queues to increase send speed while intelligently managing load at the server level. Created using PHP and shell scripting.
- Developed a social media management and publishing platform featuring integration with Facebook, Twitter, and Klout. The system downloads and calculates daily performance statistics and creates a PDF “social infographic” report. The report is designed using HTML5/CSS3, and creates a PDF using a headless browser (PhantomJS).
- Created a real-time campaign dashboard dynamically updating its display every 5-10 seconds to show users up to date statistics. Used PHP to load and cache results in real time (including unique user counts) and jQuery to serve data to the screen.
- Built a dynamic form builder allowing users to create forms with any number of fields, capture data, filter entries, and even target those entries for campaigns. Allowed the form builder to handle suppression management, validity checking, and automated cleanup of spam entries. Used PHP, MySQL, and a bit of JavaScript for the UI.
- Developed a background job processor built entirely using PHP and XML for management of scheduled and automated tasks.
- Developed a product currently used by hundreds of organizations and millions of end users across a wide range of industries, including retail, travel, financial services and utilities. Oversaw the production of over 4 major releases and hundreds of minor releases and updates.
- Created and deployed all supporting marketing and sales materials for the product, including websites, white papers, and user guides.
- Ran face to face and online (webinar) training programs for hundreds of users across dozens of client groups.
Technologies: Shell Scripting, CSS, HTML, PHP, JavaScript, Technical Leadership, Software Development, Full-stack, API Integration, Facebook API, Bots
Experience
Skills
Libraries/APIs
jQuery, Zendesk API, REST APIs, React, Node.js, X (formerly Twitter) API, Backbone.js, Facebook API, jQuery UI, QuickBooks API, Pushwoosh, Google Maps, HTML5 Canvas
Tools
AWS SDK, Amazon Simple Queue Service (SQS), Vagrant, Git, Zend Studio, Atom, ChatGPT, Claude, Slack, GitHub, Claude Agent SDK
Languages
HTML, JavaScript, PHP, HTML5, SQL, CSS3, CSS, PHP 5, Bash Script, Bash, C, TypeScript
Paradigms
Domain-driven Development, Iterative Programming, DevOps, Test-driven Development (TDD), Agile Software Development, Load Testing, REST, Model Context Protocol (MCP)
Platforms
Amazon EC2, AWS Lambda, MacOS, Linux, Windows, Amazon Web Services (AWS), NetBeans, iOS
Storage
Amazon S3 (AWS S3), Microsoft SQL Server, MySQL, JSON, Redis, CouchDB, PostgreSQL
Frameworks
AWS HA, Bootstrap, Ionic, Ionic 2, Next.js, Tailwind CSS, Ionic 3, AngularJS, PhoneGap, Zend Framework, Agentic Frameworks
Other
Technical Leadership, Software Architecture, Cloud Architecture, CTO, Software Development, Team Leadership, Enterprise Architecture, Artificial Intelligence (AI), Full-stack, Generative Artificial Intelligence (GenAI), LangChain, Architecture, Chrome Extensions, API Integration, APIs, Slackbot, Bots, Retrieval-augmented Generation (RAG), AI Agents, Shell Scripting, UI Testing, System Architecture, Web Marketing, Agentic AI, OpenTelemetry
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