Recommended expert

Andrzej Kostek

Senior Software Engineer

Andrzej Kostek
Warsaw, Poland

Experience

Jan 2021 - Present
5 years 1 month

Senior Software Engineer

UZ Leuven

  • Engineered RESTful APIs and Python-based services to integrate enterprise systems, enhancing data flow efficiency and response times by 30%.
  • Architected API modules for microservices using Java and Node.js, optimizing performance and scalability for high-volume requests in production.
  • Designed automated testing pipelines with Postman and Jest, improving API reliability and reducing bug incidence by 25% across deployments.
  • Collaborated with stakeholders to define API requirements, delivering solutions aligned with business logic and UKG Ready integration standards.
  • Optimized database queries and message queues, reducing latency by 20% for API endpoints and improving real-time data synchronization.
  • Guided junior engineers in API development best practices, testing methodologies, and integration patterns for high-quality system interfaces.
  • Integrated third-party applications and SaaS tools, ensuring seamless communication between UKG Ready systems and internal services.
  • Diagnosed performance bottlenecks in API modules, implementing caching and asynchronous techniques to enhance system throughput.
  • Coordinated cross-functional teams to align backend and front-end integrations, delivering consistent data structures and validated endpoints.
  • Engineered monitoring and logging solutions for API services, enabling faster incident response and improved operational reliability.
  • Delivered measurable improvement in system availability and API throughput, achieving 20% faster transaction processing across enterprise workflows.
May 2018 - Dec 2020
2 years 8 months

Software Engineer

Starschema

  • Developed API endpoints using Python and Node.js to support analytics dashboards, improving integration reliability by 15% for client systems.
  • Integrated multiple RESTful services with backend data stores, ensuring secure and efficient data access for complex business workflows.
  • Engineered reusable API modules to accelerate development cycles and reduce redundant coding across multiple projects and teams.
  • Collaborated with Agile teams to implement microservice patterns and CI/CD pipelines, improving deployment frequency and release predictability.
  • Implemented automated API testing frameworks with Postman and Jest, reducing error rates and improving code coverage by 18%.
  • Optimized API response times by evaluating query structures and implementing caching strategies, improving front-end performance.
  • Diagnosed integration challenges with third-party systems, proposing scalable solutions that aligned with client technical requirements.
  • Mentored junior developers on RESTful best practices, testing frameworks, and code review standards to enhance team productivity.
  • Delivered measurable outcomes in API reliability and maintainability, achieving higher client satisfaction and reduced incident tickets.
Jul 2015 - Apr 2018
2 years 10 months

Junior Software Engineer

Lingaro

  • Developed and maintained Python-based API endpoints for internal tools, improving data retrieval efficiency by 12% for analytics modules.
  • Assisted in integrating third-party REST APIs with backend systems, ensuring secure and accurate data exchange for reporting applications.
  • Collaborated with senior engineers to implement API testing procedures using Postman, increasing endpoint reliability and monitoring.
  • Contributed to unit testing and debugging, improving overall code quality and reducing integration issues for internal systems.
  • Supported team in code reviews and Agile ceremonies, learning best practices for API development and software deployment.
  • Optimized simple API workflows for data access and reporting, enhancing usability for business analysts and internal users.
  • Achieved measurable improvement in API responsiveness, gaining early recognition for efficient contributions to system integration tasks.

Summary

Senior software engineer with 10+ years of experience developing APIs, full-stack applications, and integrations using Python, Java, and Node.js. Expert in API design, RESTful services, and system integration, delivering optimized and scalable solutions for enterprise environments. Proficient in cloud platforms, CI/CD pipelines, and automated testing frameworks, ensuring robust and maintainable software delivery. Strong problem-solving and stakeholder collaboration skills, enabling seamless remote contributions to complex API-driven projects.

Skills

Programming & Frameworks:

  • Python
  • Java
  • Node.js
  • Restful Apis
  • Expressjs
  • Postman
  • Jest

Architecture & Design:

  • Microservices
  • Api-first Architecture
  • Tdd
  • Ci/cd
  • Modular Api Design

Cloud, Devops & Testing:

  • Aws
  • Azure
  • Docker
  • Kubernetes
  • Continuous Integration Pipelines
  • Automated Testing

Database & Messaging:

  • Postgresql
  • Mysql
  • Rabbitmq
  • Kafka
  • Swagger
  • Api Monitoring And Logging Tools

Soft Skills:

  • Remote Collaboration
  • Problem-solving
  • Stakeholder Communication
  • Agile Teamwork
  • Mentoring

Languages

English
Advanced
Polish
Intermediate

Education

Oct 2011 - Jun 2015

University of Warsaw

Bachelor of Arts, Computer Science · Computer Science · Warsaw, Poland

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