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Gergely Kalman, Python Developer in Málaga, Spain
Gergely Kalman

Python Developer in Málaga, Spain

Member since July 5, 2012
Gergely is a versatile CTO with a wide variety of experience in a lot of different technologies. He is able to design systems from the ground up and carry them through their lifecycle. Having managed his own tech team, he does not shy away from managing others or advising business decisions.
Gergely is now available for hire
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Portfolio

Experience

Location

Málaga, Spain

Availability

Part-time

Preferred Environment

Linux

The most amazing...

...challenge in my life has been singlehandedly writing all the code for my startup company.

Employment

  • Consultant and Blockchain Developer

    2018 - 2019
    NDA (via Toptal)
    • Refactored a large legacy codebase.
    • Helped guide business and architecture decisions.
    • Designed and implemented a distributed architecture.
    • Fixed lots of security bugs.
    • Uncovered business-level vulnerabilities.
    Technologies: Crypto, Blockchain, Django, Python

  • Senior Consultant

    2018 - 2018
    Universal Music Group
    • Refactored a Python tool.
    Technologies: Python, Google Cloud Platform (GCP)

  • Co-founder, CTO, CEO

    2014 - 2018
    Buffered.com
    • Singlehandedly designed and implemented the MVP.
    • Designed the network and APIs as well as desktop clients.
    • Ran the development team through the company's lifetime.
    • Ran the company as managing director (CEO).
    Technologies: Linux, Kivy, wxPython, Python, Django, OpenVPN

  • Software Engineer, Interviewer

    2011 - 2014
    Toptal, LLC
    • Implemented several simple websites for personal projects using Django and Jinja2.
    • Implemented OpenVPN based desktop software using wxPython, OpenVPN, and OpenSSL.
    • Interviewed a large number of candidates and overhauled the interview process.
    Technologies: Jinja, Django, OpenSSL, OpenVPN, wxPython

  • Head of Media Platform Development

    2010 - 2011
    DuoDecad, LLC, Media Platform Division
    • Worked as the only developer (for the first eight months) on an alternative video streaming platform to Adobe Flash Media Server (primary goal of the media platform division (MPD)).
    • Achieved our goal within a year using unofficial documentation of the protocol and manual reversing.
    • Designed and implemented livestream distribution and conversion architecture in Python 3.
    • Optimized to allow one node to serve more than 100 thousand clients using approximately 10Gbit/s.
    • Supported on-the-fly transcoding of incoming audio and video.
    • Benchmarked performance and moved heavy-lifting code to C.
    • Integrated several Libav libraries into Python for stream conversion.
    • Researched and assisted in hardware acquisitions for the project.
    • Devised a custom event-driven interface with custom socket handling for Python, including FLV format handlers.
    • Detected bugs in Adobe formats and in Libav format.
    • Administered MPD's machines (about 80).
    • Tuned machines for maximum network performance.
    • Lectured on IT security, MPD's project, and Python programming.
    • Iterated until peak performance of the cluster was almost 100Gb. With 30 machines, it would have been capable of completely taking over the existing streaming cluster (100+ nodes).
    Technologies: AMF, RTMP, Linux, C, Python 3, Libav

  • IT Security Specialist

    2008 - 2010
    DuoDecad, LLC, IT Security Division
    • Performed software audits, penetration tests, and stress tests.
    • Implemented failover architecture for the main website.
    • Assisted our partner company in acquiring Payment Card Industry Data Security Standard (PCI-DSS) compliance.
    • Devised company policies for PCI-DSS, developed architecture, and held educational sessions as part of IT security staff.
    • Benchmarked Linux kernel's behavior when presented with high volumes of DDoS traffic. Tuned and patched the kernel to achieve maximum resilience.
    • Worked as a member of the incident response team.
    • Developed a network analyzer in C which created real-time statistics of incoming HTTP requests and pinpointed attackers.
    • Ported old OpenSSH fork modifications to the latest version.
    Technologies: C, Linux Virtual Server (LVS), Keepalived, Iptables, Linux

  • IT Operator

    2008 - 2008
    DuoDecad, LLC, IT Security Division
    • Helped with administration of several hundred Linux machines.
    • Led support for kernel and network-related issues.
    • Wrote small scripts in bash for administrative purposes.
    Technologies: Linux

Experience

  • PCI-DSS Consultant (Other amazing things)

    Consultation and architectural help provided for Lalibco, which processed more than $500,000 daily for an Alexa top 50 website. Several bugs and security holes were uncovered in their systems. I prepared it for the PCI-DSS audit, which it passed successfully.

  • Online Payment Architect, PCI-DSS Consultant (Other amazing things)

    Helped design Escalion's (Lalib successor) system architecture from networking to services to policies and procedures. Advised on secure software practices and developed policies and procedures to keep cardholder data secure. Escalion passed PCI-DSS test and took over Lalib's transactions, which were around $500,000 each day.

  • Real Estate Scraper (Development)

    I wrote my own scraper for the largest Hungarian real estate website to get amazing deals.

  • Buffered.com (Development)

    I have created my own VPN startup called buffered.com, which I ran as CTO for three years and CEO for one year.

  • 10 Most Common Web Security Vulnerabilities (Publication)
    https://www.toptal.com/security/10-most-common-web-security-vulnerabilities
    For all too many companies, it's not until after a breach has occurred that security becomes a priority. An effective approach to IT security must, by definition, be proactive and defensive. This post focuses on 10 common and significant web-related IT security pitfalls to be aware of, including recommendations on how they can be avoided.
  • Fixing the “Heartbleed” OpenSSL Bug: A Tutorial for Sys Admins (Publication)
    https://www.toptal.com/freelance/the-heartbleed-openssl-bug-what-you-need-to-know
    A potentially critical problem, nicknamed "Heartbleed", has surfaced in the widely-used OpenSSL cryptographic library. The vulnerability is particularly dangerous in that potentially critical data can be leaked and the attack leaves no trace. As a user, chances are that sites you frequent regularly are affected and your data may have been compromised. As a developer or sys admin, sites or servers you're responsible for are likely to have been affected. Here are the key facts you need to know about this dangerous bug and how to mitigate your vulnerability.
  • With a Filter Bypass and Some Hexadecimal, Hacked Credit Card Numbers Are Still, Still Google-able (Publication)
    https://www.toptal.com/web/with-a-filter-bypass-credit-card-numbers-are-still-still-google-able
    In 2007, Bennett Haselton revealed a minor hack with major implications: querying ranges of numbers on Google would return pages of sensitive information, including Credit Card numbers, Social Security numbers, and more. While Haselton's hack was addressed and patched, I was able to tweak his original technique to bypass Google's filter and return the same old dangerous results.
  • How I Made Porn 20x More Efficient with Python Video Streaming (Publication)
    https://www.toptal.com/python/how-i-made-porn-20x-more-efficient-with-python
    Porn is a big industry. There aren’t many sites on the Internet that can rival the traffic of its biggest players. And juggling this immense traffic is tough. To make things even harder, much of the content served from porn sites is made up of low latency live streams rather than simple static video content. But for all of the challenges involved, rarely have I read about the developers who take them on. So I decided to write about my own experience on the job.

Skills

  • Languages

    C, Python, Bash, Python 3, C++, PHP, Assembler x86

  • Frameworks

    Django, Scrapy, Jinja, Qt, Django REST Framework

  • Libraries/APIs

    Libav, PyQt, OpenSSL, AMF, Kivy

  • Tools

    OpenVPN, Scraping Hub, Git, Terraform, Ansible, Packer, wxPython, Keepalived, Linux Virtual Server (LVS)

  • Paradigms

    REST, Object-oriented Programming (OOP), Imperative Programming, Event-driven Programming, DevOps, Penetration Testing

  • Platforms

    Linux, Docker, AWS EC2, Amazon Web Services (AWS), Raspberry Pi, Blockchain, Proxmox, AWS Lambda, Windows, Google Cloud Platform (GCP), MacOS

  • Storage

    AWS S3, Memcached, Redis, MySQL

  • Other

    Freelance Developer, Ethernet, TCP, UDP, SSH, Code Auditing, Iptables, Software Architecture, Scraping, System Administration, SaaS, Web Development, System Security Developer, Systems Administration, AWS, Leadership, Embedded Hardware, Internet of Things (IoT), Embedded Software, WordPress Plugins, Serverless, RTMP, Crypto

Education

  • Bachelor's degree in Computer Science
    2005 - 2007
    Eotvos Lorand Science University - Hungary

Certifications

  • AWS Certified Solutions Architect - Associate (SAA)
    NOVEMBER 2019 - NOVEMBER 2022
    Amazon Web Services (AWS)

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