Greg Kosmidis, Developer in Larnaca, Cyprus
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Greg Kosmidis

Verified Expert  in Engineering

APIs Developer

Larnaca, Cyprus
Toptal Member Since
July 21, 2021

Greg is a senior software developer with six years of experience building on the web. He is a back-end-heavy full-stack developer with experience across various stacks. Greg has worked on tens of projects, from simple presentation websites to modular e-shops, from complex booking systems to enterprise banking apps, and anything in between. He also has experience performing requirements analysis and leading teams to implement projects in an efficient and timely manner.


PHP, Laravel, Blade, Tailwind CSS, Laravel Livewire, React, Next.js, Redis...
Laravel, React, Docker, CI/CD Pipelines, MySQL, ELK (Elastic Stack), SQL...
Laravel, MySQL, Redis, SQL, MVC Design, PHP, Back-end, PhpStorm, Slack...




Preferred Environment

GitHub, MacOS, Slack, Web Development, JetBrains, G Suite, Docker, APIs, PhpStorm

The most amazing...

...product I've worked on and led is a CRM tool used by hundreds of agents servicing millions of customers.

Work Experience

Freelance Software Developer

2019 - PRESENT
  • Created an internal tool for a company that operates greenhouses to manage its workforce.
  • Created and launched an on-call pharmacy aggregator for Cyprus, ranking on Google's 1st page for relevant searches.
  • Provided website maintenance services for a Toptal client, an international amateur football league organizer.
  • Oversaw the development of a fitness portal and social network from analysis and architectural design to implementation.
  • Worked with a Toptal client providing eCommerce services for merchants using Shopify, Etsy, and custom integrations with shipping services, payment methods, loyalty platforms, helpdesk systems, and more.
  • Assisted a Toptal client in updating and upgrading the Node.js API used by their mobile social app.
  • Took ownership and maintained a CRM platform for a Toptal client, including customized feature development and feature planning assistance.
  • Took over and helped launch an MVP for a Toptal client built as a standalone API and SPA. The process included rearchitecting front-end and back-end elements.
  • Assumed control of a time-tracking and project management solution for a Toptal client, maintaining and expanding the system according to evolving needs.
Technologies: PHP, Laravel, Blade, Tailwind CSS, Laravel Livewire, React, Next.js, Redis, MySQL, Elasticsearch, GitHub, GitLab, Bitbucket, Open Source, cPanel, Docker, SQL, MVC Design, APIs, Back-end, Test-driven Development (TDD), Amazon Web Services (AWS), Amazon EC2, PhpStorm, Slack, Confluence, JavaScript, CI/CD Pipelines, HTML, CSS, Shopify, Etsy, Vue, Node.js, JSON, REST APIs, API Development, REST, Web Development, Full-stack, Databases, TypeScript, Apache, Linux, API Integration, PHP MVC, GraphQL, CSV, Cron, Web Applications, Facebook API, ShipStation, Stripe, Stripe API, Angular, Twilio, Background Jobs, Google Maps, Shopify API, HTML5, Architecture, Amazon S3 (AWS S3), Forge, Figma, Full-stack Development, Integration, Twig, NGINX, Front-end, CSV Export, Exports, Ubuntu, Payment APIs, eCommerce, Software Architecture, Technical Leadership, Jira, CodeIgniter, Composer, Scraping, Inertia, Leadership, JetBrains, Bootstrap, GitLab CI/CD, Twilio API, Azure, Migration, JSON Web Tokens (JWT), PDF, Freshdesk, SDKs, Loyalty Programs, Enterprise Loyalty Programs, Adobe Sign, Digital Signatures, Nova, Liquid, Unit Testing, Prismic, Webhooks, Laravel Forge, Sentry, SendGrid, Redux, C#, Stripe Checkout, Windows, Task Scheduling, .NET, eCommerce APIs

Senior Software Developer

2019 - 2021
  • Architected and guided a team to implement an integration with a centralized billing system.
  • Architected a solution to replace a legacy sales tracking system with an improved iteration.
  • Participated in the hiring process for new engineering resources.
  • Integrated with a tax service for existing purchasing flows.
  • Led a transition from Symfony to Laravel as the main API back end for the internal CRM tool.
  • Engineered the switch from interacting with a single external API to connecting to the entire microservices cluster the company operates.
  • Created new processes for development and quality assurance for the CRM team.
  • Architected and guided a team to implement a permission-based access control system.
Technologies: Laravel, React, Docker, CI/CD Pipelines, MySQL, ELK (Elastic Stack), SQL, MVC Design, RESTful Microservices, PHP, APIs, Back-end, Test-driven Development (TDD), PhpStorm, Jira, Confluence, JavaScript, HTML, CSS, Bitbucket, GitLab, Elasticsearch, JSON, REST APIs, PHP 7, API Development, REST, Web Development, Agile, Leadership, Full-stack, Databases, Linux, API Integration, PHP MVC, CSV, Cron, Web Applications, Background Jobs, HTML5, Architecture, Amazon S3 (AWS S3), Full-stack Development, Integration, NGINX, Front-end, CSV Export, Exports, Ubuntu, Payment APIs, Software Architecture, Technical Leadership, Symfony, Composer, Open Source, TypeScript, JetBrains, Angular, GitLab CI/CD, Migration, JSON Web Tokens (JWT), PDF, SDKs, Unit Testing, Webhooks, Redux, Windows

Web Developer

2018 - 2019
  • Helped mitigate performance issues on a large-scale news site impacted by significant traffic spikes.
  • Designed and implemented a signature management solution for banks.
  • Designed and implemented a product inventory ordering API for mobile apps.
  • Implemented an airport shuttle booking website, including the integration with payment processors.
  • Attended client meetings and performed requirement analysis and project showcases.
Technologies: Laravel, MySQL, Redis, SQL, MVC Design, PHP, Back-end, PhpStorm, Slack, JavaScript, HTML, CSS, Bitbucket, JSON, REST APIs, PHP 7, REST, Web Development, Full-stack, Databases, Apache, Linux, API Integration, PHP MVC, APIs, CSV, Web Applications, Background Jobs, Google Maps, Bootstrap, SCSS, HTML5, Architecture, Full-stack Development, Integration, Front-end, Ubuntu, Payment APIs, Software Architecture, jQuery, Custom CMS Development, Composer, Open Source, Blade, API Development, JetBrains, NGINX, CSV Export, Exports, JSON Web Tokens (JWT), PDF, SDKs, Unit Testing, Windows

PHP Developer

2017 - 2018
SK Webline
  • Added support for multiple languages to existing CMS in an SEO-friendly way.
  • Created new modules such as a sitemap generator and an infinite scrolling container.
  • Integrated with various payment processors for eCommerce and booking systems.
  • Introduced on-demand caching for content-heavy websites.
Technologies: PHP, CodeIgniter, Custom CMS Development, MySQL, jQuery, SQL, MVC Design, JavaScript, HTML, CSS, REST APIs, XML, PHP 5, PHP 7, REST, Web Development, Full-stack, Databases, Apache, Linux, API Integration, PHP MVC, APIs, CSV, Web Applications, Background Jobs, Google Maps, Bootstrap, SCSS, HTML5, Architecture, Amazon S3 (AWS S3), Full-stack Development, Integration, Front-end, Payment APIs, eCommerce, Software Architecture, PayPal, cPanel, Open Source, Back-end, PDF, SDKs, Windows


An all-in-one performance management solution for goal-focused retail employees. Allows managers to add their employees with their roles, add their product catalog, set goals per product, category, employee, role, and shop, track progress, and generate reports. Includes gamification with leaderboards and performance bonuses.

An on-call pharmacy aggregator for Cyprus. Pulling data from the Ministry of Health and giving users a way to quickly search, filter, and view details about available pharmacies. Supports showing entries on a map. I was the lead developer of this three-people project.

Greek Strings PHP Package
An open-source PHP package for manipulation of strings in Greek that handles transliteration and case switching. It is available as an installable Composer package on Packagist and distributed under the MIT license. Hosted on GitHub.


A client approached me requesting a way to manage their workforce, track hours worked across different projects, and generate statistics from the data. I designed and built a custom internal tool with Laravel and a simplistic front end utilizing jQuery and Bootstrap.

Fitness Social Network

Helped with the requirements analysis, architecture, and social network implementation to bring fitness trainers closer to their audiences. The platform included profiles, posting, messaging, live video streaming, and purchasing content. The stack was a Laravel back end with a Next.js front end. I was heavily involved in the planning, client meetings, division of work, reviews, and guidance for team members, as well as coding myself.

Chat API Rescue Operation

The Node.js API that a pair of native mobile apps used to relay to Twilio stopped functioning. I was brought in to investigate the cause and had to update the Twilio integration to a more recent major version to restore functionality.

Emergency Server Migration

A botched server update over a Christmas holiday brought an entire platform offline after causing irreparable damage to the existing VM. With minimal access in rescue mode, a salvage operation began to set up a new infrastructure and have the system up and running again in less than 24 hours.

Adobe Sign Integration

New feature for an existing CRM. Whenever a customer is quoted, they can visit a page to select the line items from the quote they want. After submitting, a PDF is generated and uploaded to the Adobe Sign service, and a signature request is initiated. The service handles the rest of the flow. Built with Laravel, but because the CRM has both Laravel and CodeIgniter components, there were requests with JWT going back and forth. The front end was an extension of the CRM's Angular app.

FreshDesk Ticket Populator

A small embedded FreshDesk app that accepts customer identification and pulls data from a 3rd-party API to populate ticket fields accordingly and automatically. Built with Node.js, using the FreshWorks SDK. Bundled and deployed on the client's installation directly.

ERP and Loyalty Services Integration

Automated the back end Laravel process that periodically pulls new order data from an ERP, parses it and pushes it to a loyalty service so that customers can be awarded points according to their purchases. Added support for date-and SKU-based point multipliers, on-demand pull for a specific date, and order ranges to accommodate evolving requests and altered data sets.

Leasing Payment Gateway Integration For Shopify

A company offering B2B leasing wanted to provide its services as a payment gateway inside Shopify. I built a solution that captures new orders and leverages the API of an intermediary web app (that I also built) to relay leasing requests to the 3rd-party service. Bundled into a Shopify app that can now be installed in any shop that wants to support leasing through this service.

Refactored a Voice Call System

Analyzed and refactored an automated scheduled calling system leveraging Twilio's Programmable Voice API. The system was successfully tested and launched, placing calls, passing through an IVR, and performing operations on behalf of the recipient or caller.

Cleaned up a React/Redux SPA

Taking over an MVP at a less-than-ideal stage, I cleaned up and linted the code, reduced coupling, extracted state, and eliminated continuity bugs while also improving user experience with actions such as adding a persistent loader that hooks onto Axios events to portray the current status accurately.

Set up a Subscription Service with Stripe

Set up billing for a newly launched product, leveraging Stripe Checkout for initial payments and Stripe Customer Portal for subscription management. Listening to Stripe webhooks, the app automatically adjusts user access to features according to the business logic.

Meeting Room Booking System

Added a new feature for an internal tool used by multiple companies to manage their workforces. Admins can set up meeting rooms, and people can book those rooms for meetings with overlap and overbook checks, as well as daily/weekly/monthly responsive calendar views.

Migrated a Service from .NET to Laravel

Migrated an existing service written in C#, using .NET and running on a remote Windows machine into a newer setup with PHP, Laravel, hosted on a VPS, and managed via Forge. The service itself handles sync between an ERP and a Shopify store. There was a noticeable improvement in processing speed and a significant reduction in errors and timeouts since the new codebase leverages modern practices for logging and error handling.


jQuery, REST APIs, API Development, Shopify API, React, Inertia, Vue, Node.js, Stripe, Google Maps, Liquid, Facebook API, Stripe API, Twilio API


PhpStorm, GitHub, Composer, GitLab, Bitbucket, JetBrains, Cron, Slack, Jira, Confluence, Apache, ShipStation, NGINX, GitLab CI/CD, Sentry, Stripe Checkout, ELK (Elastic Stack), Figma, Adobe Sign, SendGrid


Laravel, PHP MVC, JSON Web Tokens (JWT), Next.js, CodeIgniter, Tailwind CSS, Angular, Bootstrap, Nova, Redux, Symfony, Laravel Livewire, Twig, .NET


PHP, JavaScript, HTML, CSS, PHP 7, SCSS, HTML5, SQL, PHP 5, C#, XML, TypeScript, GraphQL


MVC Design, REST, Test-driven Development (TDD), Agile, Unit Testing


MacOS, Docker, cPanel, Shopify, Linux, Ubuntu, Amazon Web Services (AWS), Amazon EC2, Twilio, Azure, Windows


MySQL, Databases, JSON, Redis, Amazon S3 (AWS S3), Elasticsearch


Blade, APIs, Back-end, Web Development, Full-stack, API Integration, Web Applications, Background Jobs, Architecture, Forge, Full-stack Development, Integration, Front-end, CSV Export, Exports, Payment APIs, Laravel Forge, eCommerce APIs, CI/CD Pipelines, Custom CMS Development, Open Source, RESTful Microservices, Etsy, CSV, eCommerce, Software Architecture, Technical Leadership, PDF, SDKs, Webhooks, Scraping, Leadership, PayPal, Migration, Digital Signatures, Freshdesk, Loyalty Programs, Enterprise Loyalty Programs, Prismic, Task Scheduling

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