Maciej Rząsa, Developer in Rzeszow, Poland
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Maciej Rząsa

Verified Expert  in Engineering

Software Engineer and Developer

Rzeszow, Poland
Toptal Member Since
April 7, 2023

Maciej is a software engineer with over 10 years of back-end development experience specializing in distributed systems, databases, and software architecture. He is skilled in developing decoupled code, designing APIs, and text processing and has solid theoretical foundations in databases and high work autonomy. Maciej is also a seasoned technical leader, Scrum Master, and—occasionally—an instructor and speaker with an international track record.


Rzeszow University of Technology
Scrum, Agile, Workshops, Lecturing, Public Speaking, University Teaching
Ruby, Docker, Software Architecture, Public Speaking, Leadership, Jenkins...
Ruby, GraphQL, Microservices, Apache Kafka, REST, RSpec, Instrumentation...




Preferred Environment

Ruby, PostgreSQL, Docker, Linux, Ruby on Rails (RoR)

The most amazing...

...project I've completed resulted in a 400% reduction in the time it takes to set up a local integration testing environment.

Work Experience


2016 - PRESENT
Rzeszow University of Technology
  • Taught Agile Management to graduate management students.
  • Led the two-day Scrum+Jira workshop for post-graduate management students.
  • Delivered a talk titled "Writing software that matters on Behaviour-Driven Development" for computer engineering students.
  • Lectured Practical Agile for management students and "How to avoid being overwhelmed by work" for automatic control and robotics students.
  • Conducted a talk on incremental development for computer science students.
Technologies: Scrum, Agile, Workshops, Lecturing, Public Speaking, University Teaching

Principal Engineer

2022 - 2023
  • Reduced the setup time of the local integration testing environment by around 4x, saving development hours, after leading a project that adjusted a dockerized environment run on CI to be locally usable.
  • Investigated the potential replacement of PostgreSQL with AlloyDB and assessed performance gains. Performed statistical analysis of the test results in SciPy.
  • Optimized building a Docker image for a monolithic Ruby application by reducing the image size and build time using Docker's build cache on GitHub Actions.
  • Built a Jenkins CI tool that automated collecting issues that blocked the upgrade from Ruby 2.7 to 3 in a codebase of one million lines of code (LOC) developed by 200+ engineers.
Technologies: Ruby, Docker, Software Architecture, Public Speaking, Leadership, Jenkins, PostgreSQL, Python, Kanban

Senior Back-end Developer & Scrum Master

2019 - 2022
  • Worked on a Ruby application with 1+ million LOC, extracting a service from the monolith, improving the development experience for an engineering organization of hundreds of developers.
  • Led the GraphQL API monolith extraction to a service, proposing a process that scaled to 15 people, allowed minimal management overhead, and coordinated the production rollout. The API handled around 300 requests per minute with 100 GraphQL types.
  • Migrated a REST API to GraphQL, optimizing it along the way, reducing the response time and the number of requests sent from the client side. Proposed cutting the scope to meet a tight deadline.
  • Implemented join fields in Chewy, an Elasticsearch framework for Ruby, to support new versions of Elasticsearch.
  • Eliminated loading issues that blocked development by iteratively solving constant loading issues during service extraction and sharing learning with the team.
  • Instrumented internal GraphQL API and created a dashboard with insights about API performance.
  • Optimized the team process as Scrum Master, reducing the time required for meetings.
  • Shared knowledge with the team in numerous presentations and blog posts, covering topics such as regex performance, the extraction process, and API optimization.
  • Conducted over 50 technical interviews for software engineer and architect roles.
Technologies: Ruby, GraphQL, Microservices, Apache Kafka, REST, RSpec, Instrumentation, Distributed Systems, Leadership, Scrum, Scrumban, Kanban, Agile

Senior Ruby Developer

2016 - 2019
  • Expanded statistics, added format transformations, and improved file segmentation on a text processing service handling 1+ million words per day written in Java and JRuby.
  • Reduced cost of change and facilitated daily maintenance by refactoring critical workflow with a 6-year-old Ruby codebase according to CQRS and event sourcing principles.
  • Developed data import and export using industry and de-facto standards, such as TMX, XLIFF, and XLSX.
  • Detected and fixed concurrency issues in RubyGems using MongoDB event store and application-level lock.
  • Worked with Okapi Java localization and translation frameworks, adjusting the internals to fit the project's needs.
Technologies: Ruby, Ruby on Rails (RoR), RabbitMQ, MongoDB, REST, GraphQL, Elasticsearch, Microservices, JavaScript, React, JRuby, Docker, CQRS, Distributed Systems, Regex

Team Leader

2014 - 2016
PGS Software
  • Pioneered a Ruby developers team in PGS Software, growing the team from a solo developer to a mix of seven senior and junior engineers.
  • Expanded the team by hiring and mentoring team members and tutoring interns. Led internal workshops and conducted one-on-one meetings, providing feedback and helping engineers grow.
  • Estimated projects for the pre-sales process and discussed prospects with potential clients.
  • Led the design and implementation of Ruby on Rails projects, exposing REST APIs for mobile applications.
Technologies: Ruby, Ruby on Rails (RoR), JavaScript, Cucumber, REST, Scrum, Technical Hiring, Leadership

Software Developer

2011 - 2016
PGS Software
  • Led the Ruby ERP app development with an Android client. Organized a cross-functional team of mobile, back-end, and QA engineers to deliver new features in close collaboration with the client and decomposed and scaled a data synchronization REST API.
  • Designed and built a Ruby travel application. Migrated infrastructure from VPS to PaaS (Heroku/S3), scaling it from 2 to 1,000 requests per minute.
  • Developed a Java application using Spring and Hibernate with a replicated server environment in MySQL and HAProxy.
  • Devised and developed a Java video transcoding back end with JMS-ActiveMQ, GlusterFS, and FFmpeg. Implemented secure video streaming with Red5.
Technologies: Java, Spring, MySQL, Red5, Ruby, Ruby on Rails (RoR), RSpec, Capybara, PostgreSQL, Heroku, Linux, REST, JavaScript, AngularJS

System & Network Administrator

2009 - 2011
Zakład Usług Technicznych
  • Created a replicated server environment based on virtualization with Xen and KVM and advanced storage management with LVM and DRBD.
  • Managed ISP network infrastructure and gateway servers.
  • Collaborated with stakeholders in planning network enhancements.
Technologies: Linux

I contributed to an open source by revamping the support of nested structures in Chewy—a high-level Elasticsearch Ruby framework—from mappings to the join field. This required analyzing the current state of the code, enhancing test coverage, refactoring, and switching to different Elasticsearch APIs.

Ruby – BigDecimal
I resolved several issues in Ruby's BigDecimal, which is part of the Ruby standard library, through contributions such as:

• Improving the documentation, see
• Fixing the code, see
• And resolving doubts, see

Service Extraction

I migrated an internal Rails API from REST to GraphQL, monitored it, and optimized bottlenecks, reducing the response time and the number of requests sent from the clients. I also led the extraction of another GraphQL API—with about 100 types—from a monolithic Rails application to a service. Additionally, I coordinated work shared between two teams and scaled the extraction process to accommodate a growing headcount of 15 engineers.
2006 - 2011

Master's Degree in Computer Science

AGH University of Science and Technology - Kraków, Poland


Certified Kubernetes Application Developer (CKAD)

Cloud Native Computing Foundation (CNCF)


Professional Scrum Master I


DELE Diploma – Spanish Level B2 Certification

Instituto Cervantes




RSpec, Cucumber, RabbitMQ, Jenkins


Ruby on Rails (RoR), Capybara, Spring, AngularJS


REST, Scrum, Microservices, CQRS, Agile, Kanban


Ruby, Regex, Java, JavaScript, GraphQL, JRuby, Python


Docker, Linux, Apache Kafka, Heroku, Kubernetes


PostgreSQL, MongoDB, Elasticsearch, MySQL


Software Development, Leadership, Public Speaking, Workshops, Lecturing, University Teaching, Distributed Systems, Domain Modeling, Red5, Technical Hiring, Instrumentation, Software Architecture, Scrumban, Languages

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