Gergo is available for hire

Gergo Repas

Verified Expert in Engineering

Software Developer

Budapest, Hungary

Toptal member since February 3, 2016

Expertise

Unix Linux Java Spring Agile Development JUnit Git Hibernate SQL MySQL AWS Apache Kafka Vue.js JavaScript Redis

Bio

Gergo is a Java developer with 12 years of commercial experience in the financial sector, working at investment banks and fintech startups. He co-founded SentryKit and built its back end from scratch, exiting this commercially successful eCommerce SaaS in 2021. Gergo is passionate about distributed systems, scalability, code quality, and productivity through IT automation processes.

Portfolio

SentryKit

Java, Apache Kafka, Amazon Web Services (AWS), MariaDB, Vue, Redis...

Cloudera

Java, Hadoop, Linux, Git, Unix, Unix Shell Scripting, Eclipse IDE, Apache Maven...

Kolkida Zrt

ActiveMQ, MySQL, Spring, Hibernate, Linux, Test-driven Development (TDD)...

Experience

Linux - 12 years
Java - 9 years
MySQL - 6 years
Java Message Service (JMS) - 5 years
Amazon Web Services (AWS) - 5 years
Apache Kafka - 4 years
Vue 2 - 4 years
Spring Boot - 2 years

Availability

Part-time

Preferred Environment

Git, Apache Maven, Eclipse IDE, Unix

The most amazing...

...project I've created was a fault-tolerant distributed SaaS for Amazon sellers (sentrykit.com).

Work Experience

Co-founder

2018 - 2022

SentryKit

Co-founded SentryKit and was its CTO: a SaaS platform for Amazon professional sellers, providing analytics and alerts for their Amazon sales and products.
Designed and implemented the server-side architecture:. - Event-driven architecture using Apache Kafka and Spring Boot. - MariaDB via Hibernate and JOOQ. - At-least-once, idempotent event-processing semantics. - Zookeeper-based coordination.
Built a fully distributed, fault-tolerant system. It scaled by two orders of magnitude as the user base grew.
I learn the following front-end technologies: HTML5, ES6, Vue.js, Semantic UI, npm, WebPack, Babel.
Handled continuous deployment in DevOps and managed the cloud infrastructure.
Exited from this startup and handed the training and transitioning over to the buyer's team.

Technologies: Java, Apache Kafka, Amazon Web Services (AWS), MariaDB, Vue, Redis, Java Message Service (JMS), Linux, Test-driven Development (TDD), Spring MVC, Spring Boot, SQL, jQuery, Python, Git, Unix, Unix Shell Scripting, Domain-driven Development, Eclipse IDE, Apache Maven, Mockito, ActiveMQ, MySQL, JUnit, Vue 2

Software Engineer

2017 - 2018

Cloudera

Worked on Cloudera Distributed Hadoop internally and in the Apache open-source community. I was a contributor to Hadoop’s MapReduce and YARN components.
Worked on core components (such as YARN’s scheduler), intensively using core Java, especially Java concurrency.
Provided Level-3 (engineering) support.

Technologies: Java, Hadoop, Linux, Git, Unix, Unix Shell Scripting, Eclipse IDE, Apache Maven, Mockito, JUnit, Amazon Web Services (AWS)

Java Developer

2015 - 2016

Kolkida Zrt

Acted as a key developer in the "collection" module's development for the flag-ship loan-management product.
Performed a major role in Dockerizing the development environment.
Created a static analysis tool to flag unreachable code. The framework relied on reflection where classic tools were not accurate; I made a tool that took these specifics into account.

Technologies: ActiveMQ, MySQL, Spring, Hibernate, Linux, Test-driven Development (TDD), Oracle, SQL, Git, Unix, Domain-driven Development, Eclipse IDE, Apache Maven, Mockito, JUnit, Java

Java Developer (Core)

2014 - 2014

Algomi, Ltd.

Contributed largely towards a greenfield bond trading platform for a bond exchange. I have been a main contributor since the design phase of the project.
Indispensable in establishing advanced testing and continuous deployment infrastructure, I have introduced JBehave to increase test code re-usability and simplify capturing test scenarios. I started this initiative, and it was soon followed by team-wide adoption. This change contributed to the extremely low occurrence of regression bugs.
Improved the continuous deployment process (achieved fully automated deployment, using Bamboo). We had 5-6 dev releases per day, it helped to detect a number of (typically infrastructure or config related) problems, which cannot be covered by other means of testing, and this sped up the release process as well.
Used domain driven design and the actor pattern, which resulted in a very clean and easy-to-read codebase.

Technologies: JAXB, ActiveMQ, Java Message Service (JMS), Unix Shell Scripting, Apache Solr, Oracle, JBehave, Mockito, FIX Protocol, Spring, Hibernate, Terracotta, Java, Linux, Test-driven Development (TDD), Behavior-driven Development (BDD), SQL, Git, Unix, Apache CXF, Apache Axis, Eclipse IDE, Apache Maven, JUnit

Software Developer (Risk Calculation)

2011 - 2013

Morgan Stanley

Led the renovation project of the scenario infrastructure (rewriting legacy products to Java and Scala).
Employed SOA in this project; the team and I have been replacing service implementations from the legacy A+ language to high-throughput, parallelized Java implementation.
Manned the position of desk-facing developer (on the trading floor) until early 2012. My responsibility was to enhance the functionality and data quality of scenario-related products.

Technologies: IBM MQ, Python, Spring, A+, Scala, Java, Linux, Unix, Functional Programming, Apache Maven, JUnit

Software Developer (Risk Publication)

2008 - 2010

Morgan Stanley

Enhanced the functionality and data quality of various risk feeds.
Created performance optimization of a risk feed by increasing concurrency, for which I received a 2009Q1 Budapest IT Recognition Award.
Completed the Technology Graduate Training Programme with outstanding results (four “A” rated tests, two “B”).

Technologies: A+, Java, Linux, Unix, Functional Programming

Experience

Distributed SaaS for eCommerce Sellers

http://www.sentrykit.com

Co-found a SaaS platform for Amazon Professional Sellers, providing analytics and alerts for their Amazon sales and products.

I designed and implemented the whole back end. Most important technologies: event-driven architecture using Apache Kafka and Spring Boot; data in MariaDB via Hibernate and JOOQ; at-least-once, idempotent event-processing semantics; Zookeeper based coordination, Redis, and Exodus-based caching.

Bond Trading Platform for an Exchange

I've been working on a bond trading platform that interfaces users via the FIX protocol. Internally, it uses the actor pattern, and during design, we used the domain-driven design principle, which led to a very clean and easy-to-read codebase. I used Java, Spring (IoC and Spring Boot), Terracotta, JMS (ActiveMQ), and Axis2 during this project.

Education

2003 - 2008

Master of Science Degree in Technical Informatics

Budapest University of Technology and Economics - Budapest, Hungary

Skills

Libraries/APIs

Java Message Service (JMS), Vue, Vue 2, JAXB, jQuery

Tools

Eclipse IDE, Apache Maven, Git, Apache Solr, ActiveMQ, IBM MQ

Languages

Java, A+, SQL, JavaScript, Python, Scala

Frameworks

Spring, Hibernate, Spring MVC, Spring Boot, JUnit, Mockito, JBehave, Apache Axis, Apache CXF, Hadoop

Paradigms

Functional Programming, Test-driven Development (TDD), Domain-driven Development, Behavior-driven Development (BDD)

Platforms

Unix, Linux, Apache Kafka, Amazon Web Services (AWS), Oracle

Storage

MySQL, MariaDB, Redis

Other

Unix Shell Scripting, Terracotta, FIX Protocol

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