Abdulhalim is available for hire

Abdulhalim Kara

Verified Expert in Engineering

Full-stack Developer

Location

London, United Kingdom

Toptal Member Since

August 18, 2023

Halim is a senior software engineer with 17 years of experience developing scalable and performant microservices and web and mobile applications. Passionate about using the latest technologies, he is proficient in JavaScript, Node.js, React, React Native, MySQL, Python, and AWS. Halim is also experienced in AI and excels in designing and implementing robust solutions and building cutting-edge applications from end to end.

Computer Science Web Development User Interface (UI)User Experience (UX)Front-end Back-end Serverless Amazon API Gateway Accessibility Infrastructure as Code (IaC)WebSockets Data Scraping Vanilla JS SQL JavaScript Worldpay Plaid API

Portfolio

QMetric Group

TypeScript, Node.js, Express.js, React, GraphQL, Bootstrap, REST APIs...

Eurostar

Node.js, JavaScript, TypeScript, Koa, GraphQL, Apollo Server, React Apollo...

Dosh

JavaScript, TypeScript, Node.js, MySQL, PostgreSQL, Serverless, AWS Lambda...

Experience

JavaScript - 17 years MySQL - 15 years Node.js - 8 years Serverless - 6 years React - 6 years React Native - 3 years Python - 2 years Artificial Intelligence (AI) - 2 years

Availability

Part-time

Preferred Environment

MacOS, IntelliJ IDEA, Slack, iTerm2

The most amazing...

...thing I've accomplished is successfully implementing robust solutions and enhancing the efficiency of high-volume systems with hundreds of millions in revenue.

Work Experience

Senior Full-stack Engineer

2020 - 2023

QMetric Group

Used Node.js for microservices, React and the Webpack Module Federation for micro front-end architecture, and PlantUML to create system designs and flows.
Created, estimated, and prioritized epics, scopes, and tickets based on designed diagrams.
Built payment UIs with React and TypeScript. Used React Hook Form, styled components, Storybook, React Testing Library, ESLint, Prettier, and Sentry for monitoring. All UIs were implemented with excellent accessibility support.
Performed accessibility testing using Axe and WAVE testing tools as Chrome extensions. Converted Figma, InVision, and Photoshop designs to React components using the PerfectPixel Chrome extension for pixel-perfect UIs.
Implemented payment processing with 3rd-party APIs, leveraging various AWS services such as AWS Lambda, API Gateway, WebSocket, Fargate, and DynamoDB. Applications were deployed to multi-AZs for high availability.
Used MySQL and PostgreSQL for relational data, such as policy, user, and payment transactions, and DynamoDB for NoSQL data.
Implemented GraphQL APIs using Apollo Client and Apollo Server. I also performed end-to-end tests using Cypress.
Used TeamCity initially and then transitioned to GitHub Actions for CI/CD processes, having created CI/CD configurations from scratch in a few services.
Utilized AWS CloudFormation and AWS Cloud Development Kit (CDK) for IaC and Amazon CloudWatch for observability.

Technologies: TypeScript, Node.js, Express.js, React, GraphQL, Bootstrap, REST APIs, AWS CloudFormation, AWS SDK, AWS Fargate, Amazon CloudWatch, AWS Lambda, Styled-components, TeamCity, Kibana, RxJS, React Testing Library, Enzyme, Mocha, Jest, Cypress, Babel, Webpack, Less, Sass, GitHub, GitHub Actions, Amazon Simple Notification Service (Amazon SNS), Amazon S3 (AWS S3), WebSockets, AWS WAF, AWS IAM, Docker, Amazon EC2, Amazon Elastic Container Service (Amazon ECS), Amazon Simple Queue Service (SQS), Amazon API Gateway, Amazon Web Services (AWS), Java, User Interface (UI), User Experience (UX), Accessibility, Agile Software Development, Object-oriented Programming (OOP), Jira, Architecture, SaaS, MVP Design, Microservices, Microfrontends, SQL, Microservices Architecture, CI/CD Pipelines, Figma, Front-end, Back-end, InVision, APIs, JSON, Payment APIs, Worldpay, Online Payments, Payment Gateways, Memory Leaks, Memory Management, Full-stack, API Development, Responsive Web Design (RWD), REST, NoSQL, RDBMS, API Gateways, Mobile First, Storybook, Google Analytics, Google Tag Manager, HTML5, Web Development, API Integration, Asynchronous I/O, Responsive Web Apps, Web Design, Sentry, Serverless Architecture, Lambda Architecture, Lambda Functions, Infrastructure as Code (IaC)

Senior Full-stack Engineer

2019 - 2020

Eurostar

Worked on Node.js applications for managing bookings generated by tens of thousands of daily active users.
Contributed to front-end applications for managing bookings used by internal employees from call centers, stations, and travel agencies.
Used Apollo Client with React in the front end and Apollo Server with the Koa and Express.js frameworks in the back end.

Technologies: Node.js, JavaScript, TypeScript, Koa, GraphQL, Apollo Server, React Apollo, Styled-components, Storybook, Enzyme, Cypress, Jest, Nock, Ramda, Datadog, CircleCI, GitHub, Express.js, Amazon Web Services (AWS), Amazon API Gateway, HTML, CSS, Hapi.js, Kubernetes, Agile Sprints, Jira, Booking Apps, Booking, Booking Systems, Microservices, Microservices Architecture, SQL, CI/CD Pipelines, InVision, Front-end, Back-end, APIs, REST APIs, JSON, Payment APIs, Online Payments, Digital Payments, Full-stack, React, API Development, Responsive Web Design (RWD), User Interface (UI), User Experience (UX), REST, RDBMS, API Gateways, Mobile First, HTML5, Web Development, API Integration, Asynchronous I/O, Responsive Web Apps, Serverless Architecture, Lambda Architecture, Lambda Functions, Infrastructure as Code (IaC)

Senior Full-stack Engineer

2018 - 2019

Dosh

Built highly scalable microservices using AWS Lambda and serverless technologies.
Used GraphQL for all client and back-end communications, Apollo Client for JavaScript clients, and Apollo Server within Lambda functions.
Created a GraphQL back-end for front-end architecture (BFF), serving clients and routing the requests to appropriate microservices.
Used MySQL and PostgreSQL for relational databases and DynamoDB for NoSQL.

Technologies: JavaScript, TypeScript, Node.js, MySQL, PostgreSQL, Serverless, AWS Lambda, Amazon CloudWatch, Amazon S3 (AWS S3), AWS SWF, Amazon DynamoDB, Amazon Simple Queue Service (SQS), Amazon Web Services (AWS), Vanilla JS, Amazon API, AWS Step Functions, Bitbucket, Mastercard, MVP Design, Architecture, SaaS, PayPal, PayPal API, Microservices, Microservices Architecture, REST APIs, SQL, CI/CD Pipelines, Terraform, Back-end, Plaid, Plaid API, Venmo API, APIs, JSON, Online Payments, Payment Gateways, Payment APIs, Cash Flow, Card Payments, API Development, REST, NoSQL, RDBMS, API Gateways, HTML5, Amazon Aurora, Web Development, API Integration, Asynchronous I/O, Responsive Web Apps, Early-stage Startups, Startups, Serverless Architecture, Lambda Architecture, Lambda Functions, Infrastructure as Code (IaC)

Senior Full-stack Engineer

2018 - 2018

Crossover

Rebuilt the user interface of legacy products to a standard tech stack, building and reviewing new screens with modern UI and enhanced usability.
Reviewed the code quality of UI and REST API unit tests and functional browser compatibility testing.
Enforced code quality standards through code reviews, automated testing, and continuous integration, resulting in stable and reliable software solutions.

Technologies: JavaScript, TypeScript, Angular, Bootstrap, Karma, Jasmine, TeamCity, Full-stack, Responsive Web Design (RWD), User Interface (UI), User Experience (UX), REST, APIs, HTML5, Web Development, API Integration, Responsive Web Apps, Serverless Architecture, Lambda Architecture, Lambda Functions, Infrastructure as Code (IaC)

Senior Full-stack Engineer

2017 - 2018

Parse

Architected and developed eCommerce and mobile applications using React Native.
Engaged in direct client interactions, ensuring seamless communication and understanding of project requirements.
Worked with a diverse technology stack, including AWS Services, Node.js, React, React Native, Vue, GraphQL, Docker, Kubernetes, JavaScript, GitLab CI/CD, PHP, MySQL, and Redis.

Technologies: JavaScript, React, React Native, Vue, GraphQL, Docker, Kubernetes, Node.js, GitLab CI/CD, PHP, MySQL, Redis, Laravel, Amazon EC2, AngularJS, Amazon Web Services (AWS), Next.js, Redux, Architecture, MVP Design, SaaS, Nuxt.js, MongoDB, Traefik, NGINX, WordPress, OpenCart, VPS/VDS, OVH, Stripe, Stripe API, Twilio, Twilio API, SMS, Mandrill, Stripe Payments, PayPal, PayPal API, Mobile, Mobile UI, Mobile UX, Responsive, Mobile Apps, Mobile App Development, SQL, CI/CD Pipelines, Web Scraping, WordPress API, Expo, Android, iOS, API Development, Responsive Web Design (RWD), User Interface (UI), User Experience (UX), REST, RDBMS, Mobile First, eCommerce, Stripe Connect, Marketplaces, Google Analytics, APIs, HTML5, Web Development, API Integration, Vercel, Responsive Web Apps, Web Design, Mobile Development, Early-stage Startups, Startups

Lead Software Engineer

2015 - 2016

INT Group

Provided guidance and mentorship to a team of developers, fostering skill development and promoting a collaborative and innovative work environment.
Developed and executed technical strategies aligned with business goals, leading the team to achieve product milestones and optimize performance.
Participated in the recruitment process by interviewing candidates and playing a key role in onboarding new team members.
Designed scalable and robust software architectures, ensuring long-term maintainability, flexibility, and adherence to industry best practices.
Managed project timelines, resources, and deliverables, coordinating cross-functional teams to ensure timely project completion.
Worked on web and iPad applications for international medical clients such as Bayer, Novo Nordisk, and Takeda.

Technologies: JavaScript, Node.js, Bootstrap, jQuery, PhoneGap, MySQL, MSSQLCE, .NET, HTML, CSS, Mobile, Mobile UX, Mobile UI, Mobile Apps, Responsive, Mobile App Development, Android, iOS, Responsive Web Design (RWD), User Interface (UI), User Experience (UX), REST, RDBMS, Mobile First, eCommerce, 3D, Google Analytics, APIs, HTML5, Web Development, API Integration, Asynchronous I/O, Responsive Web Apps, Mobile Development, Early-stage Startups, Startups, Cordova

Senior Full-stack Engineer

2014 - 2015

INT Group

Joined the company as a full-time developer about one year after working with them as a freelance.
Designed and developed medical iPad applications for INT Group clients.
Used PhoneGap, JavaScript, jQuery, and Bootstrap to develop iPad applications and Node.js, PHP, and MySQL for developing back-end applications.

Technologies: JavaScript, Node.js, jQuery, Bootstrap, PHP, MySQL, SQLite, Responsive Web Design (RWD), User Interface (UI), User Experience (UX), REST, RDBMS, Mobile First, eCommerce, 3D, Google Analytics, APIs, HTML5, Web Development, API Integration, Asynchronous I/O, Responsive Web Apps, Mobile Development, Startups, Cordova

Senior Software Engineer

2013 - 2014

Advancity

Worked on a startup project for an American company partnering with Advancity.
Developed the company's official mobile application, a remote education app, with Adobe Flex.
Architected and developed back-end systems with PHP, MySQL, and Apache Solr. Used AngularJS and Bootstrap for the front end.

Technologies: JavaScript, AngularJS, PhoneGap, Adobe Flex, PHP, MySQL, Apache Solr, Bootstrap, Amazon EC2, Linux, Web Scraping, Twitter API, Android, iOS, REST, RDBMS, Mobile First, Data Scraping, APIs, HTML5, Web Development, API Integration, Responsive Web Apps, Mobile Development, Early-stage Startups, Startups

Senior Full-stack Engineer

2010 - 2013

Freelance Clients

Developed and designed eCommerce and micro websites and Flash applications for different clients.
Designed and developed my 1st startup project, dukon.co, and sold it out to an Australia-based company, DreamPushers, in 2012. We set up a company in Delaware, USA, and then I sold out all my shares.
Used a diverse technology stack including Node.js, Socket.io, PhoneGap, AngularJS, Bootstrap, JavaScript, HTML, CSS, PHP, MySQL, WordPress, and Magento.

Technologies: JavaScript, Node.js, Socket.IO, AngularJS, Bootstrap, HTML, CSS, MySQL, WordPress, Magento, REST, RDBMS, Mobile First, 3D, 3D Studio Max, Marketplaces, APIs, HTML5, Web Development, API Integration, Responsive Web Apps, Web Design, Mobile Development, Early-stage Startups, Startups, Cordova, Yii

Lead Software Engineer

2009 - 2009

Voden

Provided guidance and mentorship to a team of engineers, fostering skill development and promoting a collaborative and innovative work environment.
Participated in the recruitment process by interviewing candidates and contributing to the onboarding of new team members.
Managed project timelines, resources, and deliverables, coordinating cross-functional teams to ensure timely project completion.
Developed and executed technical strategies aligned with business goals, leading the team to achieve product milestones and optimize performance.
Designed scalable and robust software architectures, ensuring long-term maintainability, flexibility, and adherence to industry best practices.
Worked directly with clients such as ING Bank, Garanti Bank, and BKM.

Technologies: JavaScript, ActionScript 3, PHP, .NET, MySQL, Active Server Pages (ASP), HTML, CSS, CodeIgniter, REST, 3D, 3ds Max, Papervision3D, APIs, Web Development, API Integration

Software Engineer

2008 - 2009

Intro Production

Developed iPad and iPhone applications for companies in the medical industry, including Novo Nordisk, Bayer, Takeda, and Boehringer.
Used PhoneGap and Objective-C for developing iPad applications.
Worked with PHP, MySQL, JavaScript, and ActionScript.

Technologies: JavaScript, PHP, MySQL, ActionScript 3, PhoneGap, Objective-C, 3D, 3ds Max, Papervision3D, APIs, Web Development, API Integration

Experience

OpenFaceID | Identity Verification with Facial Recognition

https://github.com/ahalimkara/openfaceid

OpenFaceID is an open-source identity verification project that uses facial recognition technology to provide a robust and secure solution for detecting and authenticating known faces.

This project aims to deliver a seamless and reliable user experience for identity verification in various applications.

An Edtech App for Students

https://nsinav.com

nSınav provides educational solutions to institutions and coaches, utilizing data analytics to gain insights into students' abilities and deliver personalized support. It represents a promising intersection of technology and education, where the learning experience is enriched for all parties involved.

nSınav is an edtech platform that benefits from comprehensive technologies. PHP, MySQL, and NGINX power its back-end operations, while front-end development relies on AngularJS, Bootstrap, HTML, and CSS. The platform also offers mobile accessibility through React Native, and its deployment is managed using Docker for scalability.

Skills

Languages

TypeScript, GraphQL, JavaScript, PHP, HTML, CSS, SQL, HTML5, Python, Less, Sass, ActionScript 3, Active Server Pages (ASP), Objective-C, Java

Frameworks

Express.js, Jest, Cypress, Koa, React Native, Vanilla JS, Next.js, Redux, Laravel, Nuxt.js, Bootstrap, PhoneGap, .NET, Angular, Jasmine, AngularJS, Adobe Flex, CodeIgniter, Hapi.js, PHP MVC, Yii

Libraries/APIs

Node.js, React, REST APIs, React Testing Library, Ramda, jQuery, Twitter API, Stripe, Stripe API, Twilio API, PayPal API, Vue, Stripe Connect, RxJS, Socket.IO, Amazon API, Plaid API, Venmo API, WordPress API, API Development

Tools

Amazon CloudWatch, Mocha, Babel, Webpack, React Apollo, Amazon Simple Queue Service (SQS), Amazon Simple Notification Service (Amazon SNS), AWS Step Functions, Jira, NGINX, GitLab, Sentry, AWS CloudFormation, Traefik, Terraform, Figma, Google Analytics, IntelliJ IDEA, Slack, AWS SDK, AWS Fargate, TeamCity, Kibana, GitHub, CircleCI, AWS IAM, GitLab CI/CD, Amazon Elastic Container Service (Amazon ECS), Karma, Apache Solr, Bitbucket, InVision, Plaid, Expo, Microsoft Excel, 3D Studio Max, 3ds Max, wkhtmltopdf, Cron

Paradigms

Agile Software Development, Object-oriented Programming (OOP), Responsive, Microservices, Microfrontends, Microservices Architecture, Responsive Web Design (RWD), REST, Mobile Development, Serverless Architecture, Lambda Architecture, Hosting

Platforms

AWS Lambda, Docker, Amazon EC2, WordPress, Magento, Amazon Web Services (AWS), OpenCart, Twilio, Mandrill, Mobile, Linux, Vercel, MacOS, Kubernetes, Android, iOS

Storage

MySQL, PostgreSQL, Amazon S3 (AWS S3), Amazon DynamoDB, Redis, NoSQL, RDBMS, Amazon Aurora, MongoDB, Datadog, AWS SWF, MSSQLCE, SQLite, OVH, JSON, Cloud Deployment

Other

Computer Science, Styled-components, Enzyme, GitHub Actions, Apollo Server, Storybook, Nock, Serverless, WebSockets, AWS WAF, Amazon API Gateway, Web Scraping, User Interface (UI), User Experience (UX), Accessibility, Agile Sprints, Architecture, SaaS, MVP Design, VPS/VDS, SMS, Stripe Payments, PayPal, Mobile UI, Mobile UX, Mobile Apps, Mobile App Development, Booking Apps, Booking, Booking Systems, CI/CD Pipelines, Front-end, Back-end, APIs, API Gateways, Mobile First, 3D, Marketplaces, Data Scraping, Web Development, API Integration, Asynchronous I/O, Responsive Web Apps, Early-stage Startups, Startups, Lambda Functions, Infrastructure as Code (IaC), Artificial Intelligence (AI), Machine Learning, Vector Databases, eCommerce, Design, Google Tag Manager, Angular 2, iTerm2, Mastercard, Online Payments, Payment Gateways, Payment APIs, Digital Payments, Cash Flow, Card Payments, Worldpay, Memory Leaks, Memory Management, Full-stack, Business Services, Axios, Server-side PDF Generation, PDF, Papervision3D, Cloud Architecture, Cloud Services, Cloud Infrastructure, Cloud, Cloud Migration, Cordova

Industry Expertise

Web Design

Education

2002 - 2007

Bachelor's Degree in Computer Science

Dokuz Eylul University - Izmir, Turkey

Certifications

OCTOBER 2023 - PRESENT

AWS Certified Solutions Architect – Associate

Amazon Web Services

Collaboration That Works

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