Patryk Matuszewski, Developer in Wrocław, Poland
Patryk is available for hire
Hire Patryk

Patryk Matuszewski

Verified Expert  in Engineering

Software Developer

Wrocław, Poland
Toptal Member Since
February 11, 2014

Patryk is a software engineer who loves creating new things. He develops efficient solutions to meet client requirements. He enjoys helping clients come up with clear visions of their needs. Patryk loves to make the whole development process clear and efficient, implementing the best available options for a specific problem—he has experience using approaches like continuous delivery, Scrum, TDD, ATTD, BDD, and extreme programming.

Java, Spring, Go, JavaScript, Apache Kafka, Amazon Web Services (AWS)...
Blockchain Client (NDA)
Blockchain, Decentralized Finance (DeFi), Tokenization, Ethereum...
Web3, Solidity, JavaScript, Flask, Web Development, Off-chain Development...




Preferred Environment

MacOS, Android Studio, IntelliJ IDEA

The most amazing...

...project I've worked on is the back end of the biggest worldwide VOD delivery company.

Work Experience

Lead Engineer | Blockchain Developer

2019 - PRESENT
  • Developed a production-ready solution for car collectors.
  • Collaborated closely with the client to manage dynamic changing requirements and implement them.
  • Helped back-end and front-end engineers to achieve the team goals in the best possible way.
  • Designed and implemented the event-driven architecture suitable for integrations with multiple blockchains. Contributed to various system modules and coordinated them to deliver business value.
  • Provided blockchain cutting-edge solutions to deliver the easiest possible UX for end-users. Integrated with Ethereum Mainnet to allow bridging tokens between the networks.
Technologies: Java, Spring, Go, JavaScript, Apache Kafka, Amazon Web Services (AWS), Kubernetes, Docker, Agile, Leadership, Solidity, Ethereum, Microservices, Event-driven Programming, Event-driven Architecture, TypeScript, Agile Software Development, MongoDB, Blockchain Platforms, Node.js, Cryptocurrency, Back-end

Blockchain Developer

2024 - 2024
Blockchain Client (NDA)
  • Developed a prototype solution for managing company bonds using blockchain technology on Polygon. Technology stack: Next.js, TypeScript, Solidity, HardHat, Polygon, GraphQL, PostgreSQL, Redis.
  • Used an external custody wallet management system (Fireblocks) to integrate with the application, simplifying onboarding for non-crypto users.
  • Utilized Account Abstraction (by to create more extensible account management, enabling further integrations such as KYC and sub-accounts. It offers a more seamless user experience and customizable managing accounts.
  • Created a blockchain indexer (based on to process important information in near real-time, which was then used to display portfolio details for logged-in users.
Technologies: Blockchain, Decentralized Finance (DeFi), Tokenization, Ethereum, Front-end Development, Web Development, TypeScript, Next.js, Firebug, Cryptocurrency Wallets, Polygon, Solidity, Hardhat, Account Abstraction, GraphQL, PostgreSQL, Redis, BullMQ, Event-driven Architecture, Asynchronous Programming, Agile Software Development, JavaScript, Blockchain Platforms, Node.js, Cryptocurrency, Back-end

Blockchain Wallet Engineer (via Toptal)

2023 - 2024
  • Created a module that enables transaction management for users' wallets on a gift card marketplace.
  • Integrated with Fireblocks' external custody keys management system.
  • Developed a robust system that utilizes TypeScript, PostgreSQL, and BullMQ to handle a vast volume of user transactions concurrently.
  • Collaborated closely with the team members to successfully integrate the module with an existing system.
Technologies: Web3, Solidity, JavaScript, Flask, Web Development, Off-chain Development, Ethereum, ERC-20, Cryptocurrency Wallets, TypeScript, Ledgers, Blockchain, BullMQ, ERC-721, Firebug, Agile Software Development, Blockchain Platforms, Node.js, Decentralized Finance (DeFi), Next.js, Cryptocurrency, Back-end

Software Data Engineer

2020 - 2023
Accent Technologies Inc.
  • Improved and maintained the extractor module to handle millions of emails per day.
  • Reduced operation cost of the extractor module by an order of magnitude.
  • Worked closely with the business team to improve the business value by implementing new features.
  • Helped to improve the performance and stability of the data analytics module (PySpark).
Technologies: Java, Spring, Python, Spark, Amazon S3 (AWS S3), Apache Kafka, PySpark, Cassandra, Elasticsearch, Amazon Elastic Container Service (Amazon ECS), Data Lakes, Agile Software Development, Back-end

Team Lead

2019 - 2020
Toptal Client (Gaming Industry)
  • Gathered and analyzed business requirements during the iterative process.
  • Led and managed a team of six people. Worked closely with the client and PM to define the most effective development process.
  • Worked closely with other verticals (QA and design) to create a coherent vision of the project.
  • Wrote the integration layer between the React app and the blockchain and created an authentic gaming experience for customers.
Technologies: Amazon Web Services (AWS), Web 3.0, Ethereum, PostgreSQL, GraphQL, Redux, React, Node.js, JavaScript, Blockchain, TypeScript, Agile Software Development, Solidity, Blockchain Platforms, Cryptocurrency, Back-end

Lead Developer

2018 - 2019
Toptal Client (NDA)
  • Gathered and analyzed requirements with the client.
  • Helped organize the project timeline by introducing Agile methods.
  • Worked closely with the front-end team to help integrate with the back end.
  • Planned and implemented the sync layer between the back-end application and Ethereum private network, which helped query data from the blockchain, using simple MongoDB queries.
  • Planned and implemented the back-end service, which was the gateway between the Ethereum network and the application—used an event-driven approach with Spring Cloud and Kafka solutions.
Technologies: Apache Kafka, MongoDB, Web3j, Spring Cloud, Spring Boot, Java, Quorum, Ethereum, Blockchain, Agile Software Development, Solidity, Blockchain Platforms, Decentralized Finance (DeFi), Cryptocurrency, Back-end

Senior Blockchain Engineer

2018 - 2018
  • Created an integration layer in Node.js with the BitcoinCash network.
  • Analyzed and gathered requirements with the client for a payphone-like application.
  • Created the application's design and architecture and implemented them in the working prototype.
  • Designed the REST API, which different types of clients could have used.
  • Analyzed and made plans for the future development of the application.
Technologies: Node.js, Blockchain, Bitcoin, JavaScript, Agile Software Development, Solidity, Blockchain Platforms, Cryptocurrency, Back-end

Senior Blockchain Engineer

2018 - 2018
Synkt Games
  • Worked closely with the client on the white paper, and proposed improvements to the economic model.
  • Implemented a Crowdsale contract for the project.
  • Implemented ERC20 and utility smart contracts for the project.
  • Created the full test suite for the codebase (Truffle).
  • Deployed and tested smart contracts in the private blockchain.
Technologies: Remix IDE, Zeppelin, Truffle, Solidity, Ethereum, Blockchain, Agile Software Development, Blockchain Platforms, Cryptocurrency, Back-end

Software Engineer

2017 - 2018
  • Created a flexible solution to generate questionnaires from data taken from external sources.
  • Implemented an audio/video framework for further integration with the company's AI system.
  • Worked closely with team members to gather business requirements and transform them into application features.
  • Researched Google Fit abilities which could be used to improve application usability.
  • Worked on the application's architecture and provided detailed feedback.
Technologies: Google Fit, RxJava, Android, Java 8, Agile Software Development

Technical Project Lead

2017 - 2018
  • Initialized and analyzed the business elements of a real-time web-based game project for the education sector.
  • Created and realized the plan of development using an iterative approach and tight communication with the client.
  • Analyzed and eliminated all risks and proposed the scope which gave the best outcome for the client.
  • Used highly efficient approaches (Akka, Microservices, Cassandra) to meet real-time requirements and supported multiple teams playing at the same time.
  • Proposed and implemented event sourcing architecture for the system, which generated new tools and brought about high fault tolerance and improved performance.
Technologies: WebSockets, MySQL, RabbitMQ, Cassandra, Microservices, Akka, Spring, Java, Agile Software Development, Back-end

Back-end Lead Developer

2015 - 2018
Toptal Client
  • Prepared and implemented scalable architecture from scratch.
  • Implemented an efficient scrum planning process in the project.
  • Worked as scrum master and tried to help the rest of the team understand Scrum processes.
  • Created the continuous deployment environment by implementing full automatic regression testing suites.
  • Helped to analyze and understand all business concerns and how they impact the final product.
Technologies: Amazon Web Services (AWS), Docker, Jenkins, JBehave, Google App Engine, Java EE, Java, Agile Software Development, Back-end

Lead Software Developer

2017 - 2017
  • Elicited client requirements, prepared the project plan, and helped analyze all business requirements/rules.
  • Created the UI/UX of the application based on existing iOS design, considering Material Design guidelines.
  • Implemented an effective drawing screen solution which is easy to use for kids.
  • Created a sufficient automatic testing solution, which used remote real devices to provide the best testing results for application use cases.
  • Published the application in the Play Store with two versions and minimum defect level, supporting the greatest possible number of devices and quickly resolving any existing issues.
Technologies: Espresso, Material Design, Dagger, RxJava, Android, Agile Software Development

Software Engineer

2016 - 2017
5AM Solutions
  • Helped to set up BDD strategy for an extensive testing environment.
  • Worked on microservices to create clear and consistent endpoint contracts.
  • Helped implement a data service to handle a massive amount of ingoing data using cloud solutions.
  • Used Spring templates and Feign to create communication channels between different microservices.
  • Worked on a Spring Cloud configuration to achieve the best fault tolerance and availability level under conditions specific to the domain model.
Technologies: Docker, AngularJS, Apache Kafka, Spring Cloud, Spring Boot, Spring MVC, Java, Back-end

Android Developer

2015 - 2016
  • Improved application quality by finding and resolving most critical issues.
  • Introduced Scrum processes.
  • Helped to understand how the software development process should look and started implementing a solution tailored for this specific startup project.
  • Collaborated with back-end developers to find the best options to achieve best performance from mobile and server perspectives.
  • Helped to find a business model and how to grab customers.
Technologies: Dagger, Annotations, Robolectric, Android

Back-end Lead Developer

2015 - 2016
  • Prepared and implemented scalable architecture from scratch.
  • Implemented an efficient scrum planning process in the project.
  • Assisted in finding and analyzing all business concerns.
  • Worked with mobile developers to achieve the best performance from the server side.
  • Used TDD and created a base for BDD to have a fully-integrated deployment environment.
Technologies: Amazon Web Services (AWS), NoSQL, Google App Engine, JEE, Java, Back-end

Software Engineer

2014 - 2015
Airline Company [NDA]
  • Created a robust architecture for a ticket management application for the company's customers.
  • Assisted in improving the Scrum process and was a proactive member during standups.
  • Helped with business analysis and worked closely with the client.
  • Worked and communicated in an international team in the client's workplace (abroad).
  • Implemented and released the app used by over 100,000 people worldwide.
Technologies: Calabash, JUnit, Java, Android, Back-end

Software Engineer

2011 - 2015
VOD Content Delivery Company
  • Integrated third-party platforms with the system by VXSLs.
  • Wrote unit/integration tests.
  • Maintained the existing codebase.
  • Discussed and proposed new solutions.
  • Fixed critical bugs.
Technologies: JPA, JMS, XSLT, Java EE, Spring, Java SE, Java, Back-end

Software Engineer

2011 - 2011
  • Created an integral SEO system to support existing customers.
  • Maintained existing solutions.
  • Helped to create a clear vision what should be done in the future.
  • Learned and worked in unknown previously technologies to created better solutions (no silver bullets).
  • Worked with other people in the team to achieve common goals.
Technologies: Doctrine, C#, PHPUnit, Zend Framework, PHP 5, Back-end

Blockchain IoT
An open source solution to integrate IoT into Ethereum. I am working on the contracts' implementation as well as the general idea.

Atomize Software Spin Framework

I was working on the ORM-like solution to provide functionality handling advanced filtering or searching rules for the data synchronized with the back-end. The solution had to be effective because the app processes the massive amount of the data on the client side. Also, I helped the client to decide what solution will be the best in this particular context. | Startup

We (four members in a team) tried creating software to support management of LED ad banners on the streets. We wanted to connect banner owners with advertisers and create a new way to increase profits. The project won a B2B award on Startup Weekend Poznan (2011) but was cancelled due to lack of funding after a year.

- Led a four member team.
- Handled business analysis for the project.
- Made pitches for investors.
- Implemented the back-end using cutting-edge technologies (Symfony 2, PHP 5.3, MongoDB).
- Created a suite of full automatic acceptance/unit tests (Behat, PHPUnit).
- Implemented a mobile client (Android SDK 2.3).

Newspaper Mobile App in Android

I worked on the Android mobile app for one of the most recognized newspapers in the world. My major goal was to reduce a number of bugs (the first version of the app had a couple of thousands crash reports on Crashlytics).

To achieve that, we improved the automation testing process (added more unit tests, fixed existing one), fixed all memory management issues (like invalid bitmap processing, lack resources cleaning) and identified all use cases which can cause problems. At the end of the project, the number of crashes were reduced about 70-80% and the app started getting more positive reviews in Google Play Store.

Internal Software for an Audit Company (Android 3.0)

I created an Android 3.0 application on tablets to support audit stores for a global performance improvement company.

- The application contains questionnaires that are created dynamically by a server-side application and are needed to implement an optimal solution to exchange data between a server and web application.
- I needed to create a robust software architecture to support multiple pages and dynamic views with extensive user input support (open, close, multiple-choice question, and camera support) and multimedia support (video player, etc.)
- I implemented support for many types of tablets (Samsung, Sony, Asus).

VOD Software

Worked for the largest VOD-content delivery company in the world to improve the existing system and implement new functionality.

Technologies: Java SE, JEE, Spring, XML, XSLT

Created an Android application for a Polish startup allowing users to find a nearby medical specialist.

- Led a three person team.
- Conducted business analyses with the customer (created a list of features, wireframes, and a domain model).
- Prepared a specification of a back-end API that was needed to communicate between an Android app and a back-end server (used RESTful best practices).
- Handled project management using Agile methodology and TDD.
- Implemented the application using cutting-edge Android technologies (API 4.1, AndroidAnnotations, RoboGuice, Robolectric).

Software for Analyzing Mobile Application Stats | PHP 5

I created a web platform for analyzing mobile application stats. We needed to create a complex solution to gather statistical information from many kinds of mobile applications (e.g., how much time users spend on each page or how many times users click on a banner).
- I implemented a library to communicate with a back-end API for J2ME. It featured optimized operations for low-memory devices and support for a wide range of mobile phones.
- I created a MySQL sharding module for a back-end system (PHP 5.3, MySQL). It required a scaling feature for a growing numbers of users and applications.
- I implemented a dynamic web interface on the user side (stats are updated in almost real-time).

Leagues Management Application (PHP)

Created a PHP application for a small sports company to support management football (soccer) leagues.

• Architected the app
• Deployed a small iterative process to control requirements changes
• Implemented the app based on the project and client requirements
• Set up a production environment (Apache 2, PHP FPM, ACL, MySQL)

Technologies: PHP 5.3 + Doctrine + Zend Framework 1 + Facebook API, jQuery, PHPUnit

Tax Refund Management Application

Created an application to support and manage tax refunds in the UK

- Worked directly with the client to settle all requirements
- Implemented a small iterative development process to handle changes
- Architected the app
- Implemented the app based on existing law regulations
- Set up a production environment (Apache 2, Nginx, PHP FPM, MySQL)

Technologies: PHP 5.3 + Doctrine 2 + Zend Framework 1 +
Doctrine 2 + Zend Framework 1 + jQuery + PHPUnit

BlackBerry 6 Project

I created a quiz application for an airline related company (Tech: Java 1.4, BlackberrySDK 6, Facebook API, JS, HTML). During the project, I needed to learn a completely new SDK and use this knowledge in a business environment.

- The UI implementation (JavaScript, HTML) is based on existing wireframes and included support for many types of devices.
- I created a library to communicate with Facebook API in Java 1.4. I needed to use a limited edition of Java specifications to create a robust solution to support many user behaviors, such as image uploading, adding texts to the Wall, inviting friends, and sending messages to friends. The application worked on 3G.

Android 2.2 Project

An Android 2.2 news feeder for one of the biggest broadcasting companies in the world. I needed to include support for an Arabic language-based device and fixed bugs in the existing legacy code.


Java Collections, Android API, React, Node.js, Java Servlets, React Redux, JMS, Doctrine, RxJava, Web3j, Hystrix, Backbone.js, Facebook API, jQuery, X (formerly Twitter) API, PySpark


PhpStorm, IntelliJ IDEA, Calabash, Jenkins, RabbitMQ, Remix IDE, Eureka, Apache ZooKeeper, Eclipse IDE, JHipster, Android Studio, WebStorm, Amazon Elastic Container Service (Amazon ECS), Firebug


Spring Security, Truffle, Android SDK, Spring Boot, Spring MVC, Swagger, Spring Android, Next.js, Spring, JUnit, JBehave, Robolectric, Dagger, Zend Framework, PHPUnit, Espresso, Akka, Redux, AngularJS, JPA, JavaServer Faces, Hibernate, Spark, Flask, Hardhat


JavaScript, Solidity, Java, Kotlin, TypeScript, Java SE, XSLT, PHP 5, C#, Java 8, Scala, Python, PHP, SQL, Clojure, GraphQL, Go


Continuous Integration (CI), Behavior-driven Development (BDD), Iterative Programming, Agile Software Development, Object-oriented Programming (OOP), Unit Testing, Design Patterns, Test-driven Development (TDD), Functional Programming, Cross-platform, Microservices, Concurrent Programming, Distributed Programming, Pair Programming, Domain-driven Development, Mobile Development, Agile, Event-driven Programming, Event-driven Architecture, Asynchronous Programming


Blockchain Platforms, Blockchain, Ethereum, iOS, Google App Engine, Android, Linux, Chainlink, MacOS, Java EE, JEE, Apache Kafka, Zeppelin, Kubernetes, Docker, Netflix, Amazon Web Services (AWS), Windows


Redis, MySQL, MongoDB, NoSQL, Cassandra, PostgreSQL, Google Cloud, Amazon S3 (AWS S3), Elasticsearch, Memcached, Data Lakes


Ethereum Smart Contracts, Architecture, Technical Leadership, Web Development, Full-stack Development, Front-end Development, Cryptocurrency, Back-end, Spring Cloud, Software Architecture, Decentralized Finance (DeFi), Annotations, Material Design, WebSockets, Google Fit, Quorum, Bitcoin, Web 3.0, Netflix OSS, Apache Commons, Apollo, Apollo Server, Leadership, Know Your Customer (KYC), Tokenization, Web3, Off-chain Development, ERC-20, Cryptocurrency Wallets, Ledgers, BullMQ, ERC-721, Polygon, Account Abstraction, UTXO

Collaboration That Works

How to Work with Toptal

Toptal matches you directly with global industry experts from our network in hours—not weeks or months.


Share your needs

Discuss your requirements and refine your scope in a call with a Toptal domain expert.

Choose your talent

Get a short list of expertly matched talent within 24 hours to review, interview, and choose from.

Start your risk-free talent trial

Work with your chosen talent on a trial basis for up to two weeks. Pay only if you decide to hire them.

Top talent is in high demand.

Start hiring