Kostyantin A.
Offer Kostyantin work on your next project.
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Offer work 
Chernovtsy,
Ukraine
22 days 1 hour back
available for hire
1 Safe completed
2 years back
1 client
on the service 3 years
Rating
Successful projects
Average rating
Language proficiency level
Українська: fluent
English: intermediate
Skills and abilities
Portfolio
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Internal Systems Website
Website Development
Development of a website from scratch as a single-page application (SPA) on Vue using Tailwind for building the interface.
Designing the structure of the frontend, components, and navigation.
Implementation of a lightweight PHP OOP backend for handling requests, working with forms, and server logic.
… Ensuring performance, clean code structure, and ease of future expansion.
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Backend support and development of a CRM platform
PHP
Participated in the development of a production CRM system at the stage of preparing the product for scaling and launch. The main focus was on refactoring and stabilizing the existing backend part, organizing business logic, and increasing code maintainability.
Decomposed overloaded backend modules, structured service logic, and improved data processing flows. Optimized existing processes and refined functionality in an active development environment without impacting the stability of the production environment.
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Click to Sign Module for Custom CRM System
Web Programming
Full development of the electronic document signing module "Click to Sign" from scratch for a custom-built CRM system.
Design and implementation of the module architecture.
Creation of the database structure and its integration into the existing MySQL schema.
Development of reusable and customizable document templates.
… Implementation of PDF generation, display, and signature overlay.
Integration with internal CRM data: projects, contacts, document database.
Implementation of one-time signing links with expiration and access control.
Building signing logic with status tracking, logs, and error handling.
Development of notification system (email and SMS) with templates.
Creation of front-end signing interface with responsive UX.
Testing, deployment to production, technical documentation.
Stack and technologies used:
PHP 8.3 (OOP), JavaScript, MySQL, RedBeanPHP ORM, FPDI, FPDF, Ghostscript, ImageMagick, pdftoppm, mutool, + custom utilities for PDF processing and rendering.
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Module for generating project documents for a custom CRM system
Web Programming
A module for creating project documentation based on PDF templates has been developed using structured data entry forms. The system allows for the generation of documents with automatic filling of information from the CRM (contacts, addresses, details, project parameters) with subsequent saving, versioning, and linking to the relevant entities of the system.
Server-side generation of PDF documents has been implemented with the ability to preview and adjust data before creating the final version. Validation of entered values, auto-fill logic, and preparation of documents for further signing and distribution within CRM workflows have been added.
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File management module for a custom CRM system
Web Programming
Development of a module for storing and distributing files with folder logic similar to a file system. Implemented uploading, organization, and sharing of files and directories through public links, as well as linking documents to CRM entities (projects, contacts, etc.). Additionally, implemented the creation of media files directly in the browser (audio recording, screen recording) and automatic processing of files during upload.
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Automated cryptocurrency futures trading platform
Bot Development
Development of an automatic trading system based on the Binance API with support for multiple trading strategies and flexible configuration of parameters. The platform provided simultaneous execution of several strategies with the processing of a large number of trading pairs.
A complete cycle of automatic trading was implemented: signal processing, order execution, monitoring of open positions, and risk management (including trailing stop logic).
… Architecture of the solution:
Python service for executing trades and processing signals,
PHP + JavaScript web interface for monitoring and management,
MySQL as a shared data layer between services.
The system supported parallel operation of strategies, high-load processing of trading pairs, and fully automated management of trading operations.
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Service and billing control panel for SMS service
PHP
Participation in the development and further improvement of the internal service management system, billing, and transaction accounting. Working with the backend part of the existing system: supporting functionality, stabilizing operations, and gradually enhancing business logic in the context of active product development.
Tasks included refining the API, optimizing data processing, fixing critical system nodes, and adapting the code to new business requirements.
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Work on the backend of a custom CMS for a blog platform
PHP
Optimization and refactoring of the existing PHP code have been carried out, improving the structure of the backend logic and the stability of the system's operation. Enhancements to the content management functionality and the performance of the administrative part have been completed. An AI agent based on the OpenAI API has been integrated for generating, editing, and assisting in the processing of text content directly within the CMS.
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Refactoring the backend of a custom CMS for an online store
PHP
Refactoring and modernization of the PHP backend of a custom online store engine. Optimization of legacy code has been carried out by decomposing large procedural files into functional modules by purpose. Database restructuring has been performed: normalization of the structure, implementation of pivot tables, indexing, and configuration of relations. Secure data migration from large tables to the new structure has been implemented without disrupting system operation. Overall performance optimization and code cleanup have been conducted.
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Updating and optimizing the backend of a custom PHP online store
PHP
The procedural code has been reorganized by separating the logic into distinct functional components. Improvements have been made to the database structure: normalization of tables, implementation of many-to-many relationships, addition of indexes, and optimization of SQL queries. Careful migration of data to the updated structure has been carried out, along with an overall increase in the stability and performance of the system.
Reviews and compliments on completed projects 1
19 October 2023
33 USD
Working with a web site on pure php
Quality
Professionalism
Cost
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Deadlines
Everything is fast and clear! Thank you for work!
Liubomyr Lukaniuk
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