Backend Software Engineer · London, UK

Oleksandr Kashytskyi

I build scalable, well-tested backend systems.

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alex — backend software engineer

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Node.js · TypeScript · PostgreSQL · Redis · Docker · EC2

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B2B B2C Fintech E-commerce Enterprise Systems

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years in production: 3+; years in production
users on apps I’ve worked on: 30M+; users on apps I’ve worked on
uptime on production systems: 99.9%; uptime on production systems

About

Hello and welcome

I am a Backend Software Engineer with 3+ years of commercial experience designing and scaling Node.js/TypeScript systems for B2B, B2C and fintech products, including applications serving 30M+ users at 99.9% uptime. I’m strong in REST API design, PostgreSQL performance, caching and payment integrations, with full-stack ability in React and Next.js.

Working at GoodRequest I’ve delivered robust solutions for companies like Notino, KIA, and Aivodot — designing REST APIs, optimizing databases, implementing caching strategies, and integrating complex workflows. I work across the full backend stack, from Node.js, TypeScript, and Express.js to PostgreSQL, Redis, Docker, and AWS, ensuring clean, maintainable, and well-tested code that powers real-world systems.

Today I work as a self-employed full-stack developer, mainly with clients on Upwork, while building FlowersShop, a multi-language e-commerce platform, from requirements to deployment. Its public beta is open source; active development continues in private repositories.

Beyond professional projects, I build personal and open-source applications that show my ability to tackle complex logic, ship functional prototypes, and experiment with new technologies. With a solid foundation in algorithms, design patterns, and software architecture, I create solutions that are reliable, efficient, and user-focused.

B2BB2CFintechE-commerceEnterprise Systems

What I do

Design and maintain scalable REST APIs
Build and evolve Node.js backend systems
Optimise databases and data-heavy workflows
Refactor legacy systems safely in production
Collaborate in cross-functional Agile teams

Selected work

Featured projects

From production systems used by millions to personal products built end-to-end.

All projects →

Admin, product editor, shop and order details

Personal

Flowers Shop

Multilingual e-commerce platform with payments, shipping and an AI assistant.

TypeScript · Node.js · Express.js +28

Commercial · GoodRequest

Notino

Backend services for one of Europe’s leading beauty e-commerce platforms.

TypeScript · Node.js · Express.js +25

Commercial · GoodRequest

Aivodot

Personalised investment guidance tailored to each investor’s risk profile.

TypeScript · Node.js · Express.js +22

Career

Experience

Jun 2026 – Present
Jun 2026 – Present
Upwork
Freelance Software Engineer · Remote
Backend and full-stack work for clients through Upwork, and Flowers Shop: a multilingual e-commerce platform for a family flower business, built end to end (public beta; active development continues in private repositories).
Flowers Shop
Jan 2026 – May 2026
Jan 2026 – May 2026
Oud Technologies
Volunteer Backend Developer · Remote
Refactored the TypeScript backend of Tech Academy, an educational web platform, improving code structure, maintainability and architecture.
Tech Academy
Mar 2022 – Aug 2025
Mar 2022 – Aug 2025
GoodRequest
Backend Developer · Košice, Slovakia
Maintained and extended high-traffic modules for Notino across multiple EU markets. Designed and documented REST APIs, optimised PostgreSQL queries and caching, integrated Stripe subscriptions and webhooks, and introduced Sentry monitoring. Joined through the GoodRequest Academy backend bootcamp (Mar–Jul 2022).
Notino Aivodot KIA Benzinol express-joi-to-swagger
May 2020 – Mar 2022
May 2020 – Mar 2022
Self-employed
C Programming Tutor · Košice, Slovakia
Taught C to around 20 university students one-to-one: algorithms, pointers, memory management and debugging.

Education

Sep 2025 – Aug 2026
MSc Web Development
University of Roehampton, London
First class honours
Dissertation: a modern e-commerce application with multilingual support, online payments and shipping integration.
Sep 2019 – Jul 2022
BSc Computer Science
Technical University of Košice
First class honours
Modules: Algorithms and Data Structures, Operating Systems, Software Architecture, Component-Based Development.
Thesis: Implementation of OpenAI environment

References

Recommendations

Written recommendations from people I’ve worked and studied with, on my LinkedIn profile.

Martin Durny
Former Team Lead · GoodRequest
Read Martin’s recommendation on LinkedIn
Jose Paredes
MSc Supervisor · University of Roehampton
Read Jose’s recommendation on LinkedIn

Tech stack

Tools I use every day

Click any tile to see what I use it for and where.

All skills →

BullMQ
Expert
Redis-based queue system for background jobs and async processing.
Backend
Used in
- Notino
- Aivodot
C
Expert
Low-level language used to understand memory management and system-level programming.
Languages
Chai
Expert
Assertion library used to validate application behavior in tests.
Testing
Used in
Docker
Expert
Containerization platform ensuring consistent runtime environments.
DevOps · Backend
Used in
ESLint
Expert
Static analysis tool enforcing code quality and consistency.
Others
Used in
Express.js
Expert
Minimal Node.js framework for building REST APIs with middleware-based architecture.
Backend
Used in
Git
Expert
Version control: branching strategies, rebasing, code review and clean history.
Project Management · DevOps
GitHub
Expert
Version control and collaboration platform for managing source code.
Project Management
HTML
Expert
Markup language defining semantic structure of web pages.
Frontend
Used in
i18next
Expert
Internationalization framework for managing translations and multi-language support.
Backend · Frontend
Used in
JavaScript
Expert
Core language of the web used across frontend interfaces and backend services.
Languages
Used in
- CityDesk
- Weather App
Joi
Expert
Schema-based validation library ensuring API request data integrity.
Backend
Used in
JWT
Expert
Stateless authentication mechanism using signed tokens.
Security
Used in
Mocha
Expert
JavaScript testing framework for unit and integration tests.
Testing
Used in
Node.js
Expert
JavaScript runtime for building fast, scalable backend services and event-driven APIs.
Backend
Used in
Nodemailer
Expert
Transactional emails — bookings, invitations, password recovery — rendered from EJS templates.
Backend
Used in
PostgreSQL
Expert
Advanced relational database focused on data integrity, performance, and complex queries.
Storage
Used in
Postman
Expert
Tool for testing, debugging, and documenting REST APIs.
Testing
Prettier
Expert
Opinionated code formatter keeping style consistent across teams.
Others
Used in
- express-joi-to-swagger
- Backend Express Template
Prisma
Expert
Type-safe ORM simplifying database access and schema migrations.
Backend
Used in
Python
Expert
General-purpose language used for backend services, scripting, and automation.
Languages
Redis
Expert
In-memory data store used for caching, queues, sessions, and real-time data.
Storage
Used in
Sequelize
Expert
ORM providing model-based access to SQL databases.
Backend
Used in
Supertest
Expert
HTTP assertions for end-to-end testing of Express endpoints together with Mocha and Chai.
Testing
Used in
Swagger
Expert
Tooling for designing, documenting, and testing REST APIs using OpenAPI specifications.
Backend · Project Management
Used in
TypeScript
Expert
Strongly typed JavaScript superset improving code safety, refactoring, and scalability.
Languages
Used in
Winston
Expert
Structured logging library for Node.js applications.
Monitoring
Used in

Personal library

Books that shaped how I build

Open library →

The C Programming Language
Brian W. Kernighan
Programming Languages
Classic book teaching C fundamentals, idiomatic C programming, and foundational programming concepts.
Takeaways
Pointers, memory management, structured programming, and clean coding practices.
The C++ Programming Language
Bjarne Stroustrup
Programming Languages
Comprehensive guide covering C++ syntax, object-oriented programming, templates, and the STL.
Takeaways
OOP principles, templates, STL, memory management, RAII, and idiomatic C++ patterns.
Java: A Beginner’s Guide
Herbert Schildt
Programming Languages
Beginner-friendly introduction to Java covering core syntax, object-oriented concepts, and basic libraries.
Takeaways
Java syntax, OOP principles, basic GUI development, exception handling, and standard libraries.
Effective Java
Joshua Bloch
Programming Languages
Advanced guide on writing robust, maintainable, and high-performance Java code with best practices.
Takeaways
Design patterns, API usage, performance optimization, and writing clean, efficient Java code.
C#: The Complete Reference
Herbert Schildt
Programming Languages
In-depth reference covering C# language features, .NET integration, and practical programming examples.
Takeaways
C# syntax, LINQ, collections, .NET frameworks, and practical backend application development.
JavaScript & jQuery
Jon Duckett
Programming Languages
Guide to JavaScript basics, DOM manipulation, event handling, and creating interactive web applications.
Takeaways
JavaScript syntax, DOM API, event handling, asynchronous programming, and basic web interactivity.
HTML & CSS
Jon Duckett
Web Development
Introduction to building web pages with HTML structure and styling them with CSS, including responsive design.
Takeaways
HTML semantics, CSS layout techniques, styling, responsive design, and web design best practices.
Git Magic
Ben Lynn
Software Development
Concise guide to using Git for version control, branching, merging, and collaborative workflows.
Takeaways
Git commands, branching strategies, conflict resolution, and efficient version control practices.
Grokking Algorithms
Aditya Bhargava
Software Development
Illustrated guide for learning algorithms and problem-solving with visual examples and exercises.
Takeaways
Sorting, searching, recursion, Big O notation, and algorithmic thinking for coding challenges.
Design Patterns
Erich Gamma
Software Development
Classic book introducing design patterns for reusable, maintainable, and modular object-oriented software.
Takeaways
Key patterns such as Singleton, Observer, and Factory, and strategies for clean software architecture.
Deep Reinforcement Learning with Python
Sudharsan Ravichandiran
AI
Practical guide to reinforcement learning algorithms and agent-based models using Python.
Takeaways
Q-learning, policy gradients, neural network integration, environment design, and agent training.
Python Machine Learning
Sebastian Raschka
AI
Guide to implementing machine learning algorithms and understanding models using Python libraries.
Takeaways
Supervised and unsupervised learning, scikit-learn, model evaluation, and feature engineering.
Hands-On Intelligent Agents with OpenAI Gym
Praveen Palanisamy
AI
Hands-on reinforcement learning projects using OpenAI Gym, Python, and practical exercises.
Takeaways
Environment creation, agent training, policy evaluation, and applying RL concepts to practical tasks.
Node.js Web Development
David Herron
Backend & Databases
Guide to building server-side applications using Node.js, Express, and asynchronous programming.
Takeaways
Server-side JavaScript, REST APIs, routing, middleware, async programming, and the Node.js ecosystem.
Designing Data-Intensive Applications
Martin Kleppmann
Backend & Databases
Guide to building scalable, reliable, and maintainable data systems for modern applications.
Takeaways
Distributed system principles, data modeling, consistency models, and fault-tolerant architectures.
PostgreSQL
Pavel Luzanov
Backend & Databases
Comprehensive guide to PostgreSQL covering queries, indexing, transactions, and database design.
Takeaways
SQL queries, indexing, transactions, performance tuning, and database best practices.
SQL Antipatterns
Bill Karwin
Backend & Databases
Guide to common SQL mistakes and how to avoid them in schema design and queries.
Takeaways
Pitfalls in database design, query optimization, and maintaining data integrity.
Arduino Microcontrollers Programming
Ulli Sommer
Embedded & Operating Systems
Practical guide to programming Arduino microcontrollers and building electronics projects.
Takeaways
Microcontroller programming, working with sensors and actuators, and small electronics projects.
Modern Operating Systems
Andrew S. Tanenbaum
Embedded & Operating Systems
Comprehensive guide to operating system design: processes, memory, scheduling, and file systems.
Takeaways
Process management, CPU scheduling, memory handling, file systems, and OS architecture concepts.