Sergey Vasilyev

  • Phone: +49 157 3232 0684
  • Email:
  • Location: Berlin, Germany.
  • Work permit: Niederlassungserlaubnis; ex-owner of Blaue Karte EU (Germany).


Skilled developer with 15+ years of experience. Master of Computer Sciences majored in Distributed Computer Systems. Consistently and proactively demonstrates technical leadership, architectural and product design skills through to expertise in:

  • Technology and infrastructure management as a CTO/CIO.
  • Building & leading & managing the teams of software developers.
  • Python development, software design, infrastructure automation.
  • A long time ago, in a galaxy far far away: PHP, and lots of other languages & frameworks.

Author of Kopf, a Kubernetes Operators Pythonic Framework (

Keywords: Python, Pytest, MySQL, Postgres, DevOps, Kubernetes, Docker, AWS, SaaS, PaaS, IaaS, Cloud, etc.


Senior Backend Engineer in Pricing & Forecasting
Zalando SE

One of the biggest European e-commerces and a fashion platform; ~15000 employees.
Feb 2018 – now. Berlin, Germany.

Maintaining & refactoring the Machine Learning platform for the article sales forecasting. Migrating the data processing and sales forecasting pipelines to Kubernetes. Authored Kopf, a Kubernetes Operator Pythonic Framework: to orchestrate the workload in ML-/domain-terms.

Won a “Geeks of the Week” award (with a colleague) at the HackWeek (an in-house hackathon) for the ML Model Management via Kubernetes CRDs.

Mentoring junior and middle Software Engineers and advising the Data Scientists on best software development practices, CI/CD workflows, software architectures, tips and tricks.

Senior Python Developer / TeamLead Integration
ProfitBricks GmbH (renamed to Ionos SE)

Could computing IaaS company; 100+ employees.
Sep 2015 – Jan 2018. Berlin, Germany.

Developing an ecosystem (frameworks, toolkits, CLIs/UIs, infrastructure, guidelines, documentation, etc) for integration- & performance- & endurance- & stress-testing of the cloud (IaaS), used by the QA engineers & developers to test their components of the cloud, and the cloud as a whole from the customer point of view.

Leading a team of 3 Python developers, plus a workgroup of QA engineers from different teams in order to utilize the developed toolkits and to achieve the higher level of QA automation.

Senior Software Engineer in QA Automation/Infrastructure

International backup solution provider; 700+ employees.
Nov 2014 – Aug 2015. Moscow, Russian Federation.

Maintaining and improving the infrastructure and the tools for the QA automation team (as an internal customer), which includes hypervisors, virtual machines provisioners, task schedulers, results gathering and aggregation (ElasticSearch, Kibana, Django, etc). Deployed the monitoring system for the infrastructure (Zabbix).

Designed the solution, found the tools and started a stage-by-stage removal of the technical debt in the whole QA & QA Automation system architecture. Created a couple of auxiliary utilities for developers & automation engineers.


Real estate web portal and aggregator; 80 employees.
July 2012 – February 2014 (1 year 8 months). Moscow, Russian Federation.

While keeping the responsibilities of the Head of Development Department, also took control over the IT department, which includes the web portal infrastructure, the intranet infrastructure, and the technical support.

With IT team:

Reworked the whole infrastructure of both web portal and office infrastructures: virtualized everything that could be virtualized with no harm to the system, reorganized the servers and their roles, thus achieving better utilization of hardware resources (less idling of CPU/RAM/IOPS) and isolation of the servers (both for security, and to control their resource consumption).

Moved most of the infrastructure from ancient collocated bare-metal servers in Russia to rented modern servers in Europe (including the refactoring of the infrastructure so it is movable). This reduced the monthly hosting bill by approximately 40-50% and long-term TCO by 50-70%. Also, the maintenance and upgrade of the hardware were outsourced, so that the IT department could focus on the more important tasks and the shortage of the computational resources to the moment was eliminated.

Built the technical support for the customers, partners, and for the intranet services. Partially automated it.

With development teams:

Continued all the things regarding the software development (see below for Head of Development Department): system design, infrastructure and platform services, control of the development process, etc.

Head of Development Department

Real estate web portal and aggregator; 80 employees.
August 2010 – July 2012 (2 years). Moscow, Russian Federation.

Managed a department or front-end, back-end and database developers, QA specialists. Initially, there were 13 employees (8 on staff and 5 freelancers). Due to company growth in 2012 and renewal of a team, found and hired 12 more web developers in 6 months, ending up to 27 employees by the end of 2012 (with no HR at hand).

Built the processes to work and effectively communicate with a distributed team of web developers, 80% of whom are spread across the country (yet working full-time and on staff).

Proposed and initially implemented significant refactoring of the system architecture to achieve basic scalability and better code flexibility & maintainability. Three-tier service oriented architecture (SOA) was built while keeping the old system up and running during the ongoing 2-year migration process. Backends and frontends are communicating via Apache Thrift RPC protocol. The backend consists of few isolated applications running on self-made Thrift Application Server written in Python; the frontends run on PHP.

Maintained legacy PL/SQL code in Oracle Database: modified it when necessary for better performance and to remove errors, optimizing data storage and some database options.

Controlled the development process of 5 to 7 teams of the developers for compliance with the overall system design, available solutions, and company standards, gradually switching it to SOA (Service Oriented Architecture), and removing the old legacy (monolithic, expensive, totally non-scalable).

Directly managed the development of some company’s long-term projects: mobile applications, back-office import/export/crawling systems, intranet content management applications, internal back-end and infrastructure services.

Was in charge of architectural and system design solutions for the whole system: top-level components and protocols, connections with third-party software, stability, security, performance, etc.

Senior Python Developer

Real estate web portal and aggregator; 50 employees.
February 2010 – August 2010 (7 months). Moscow, Russian Federation.

Lead a team of three Python developers. This includes task management and prioritization, features and milestones planning, control of deadlines, consultations, and advice for architectural solutions. The team works on back-office admin applications and on the real estate data mining system.

Developed few prototype real estate applications and services for Nokia mobile phones. They allow browsing and viewing of real estate advertisements as a list or on a map, so as filtering them with customizable criteria. The service is launched at (adopted for Nokia’s WebKit built-in browser, compatible with Firefox).

Python Developer

Real estate web portal and aggregator; 50 employees.
September 2009 – February 2010 (6 months). Moscow, Russian Federation.

Designed (from scratch) a back-office system for automated data mining of third-party real estate data sources to company’s web portal. The system consists of three primary parts: fetchers, converters, uploader. Dataflow starts from fetching the files from external sources, then continues to parse them and converting them into company’s format, then finishes with uploading them to the database and photo storage.

Implemented this system with Python 2.6. A core of the system is a framework with few automated entry points and an extensible set of libraries for normalization and validation of data values. The rest of the system is a collection of specific format descriptions made by a team of back-office developers.

Developed approximately 10 back-office admin applications and front-office widgets. Supported and improved approximately 10-15 applications of other developers. All were made with Python 2.6 and Django 1.1, and with Django 1.2 later. Most of them include specially developed Django widgets, modified admin forms, additional validation and business logic.

Senior PHP Developer
Project 2000+

SaaS web site & application constructor (startup); 5 employees.
July 2008 – May 2009 (11 months). Moscow, Russian Federation.

Developing a dating app with PHP. Mostly backend: databases, ORM, caching, performance, scaling.

PHP Web Developer
Howard Design Studio

Web design and web development agency; 7 employees.
August 2007 – July 2008 (1 year). Moscow, Russian Federation.

Developed studio’s content management system (CMS), universal content-handling tools (typographic and similar). Built server and client sides of multiple web-sites. PHP 5 and MySQL 5.

PHP Web Developer

August 2005 – August 2007 (2 years).

Developed own Content Management System (CMS). PHP 5, MySQL 5, XML+DOM+XSLT as template engine. Used this CMS in few web-sites.

System Administrator
KrasLAN Internet Service Provider

November 2003 – August 2005 (1 year 10 months). Krasnoyarsk, Russia.

Developed network and server monitoring tools, billing maintenance scripts. Administered ISP servers (FreeBSD). Built and managed an ISP help desk: technical consulting by phone, email and in the office. Created and applied routines and procedures for coordination of network maintenance personnel.

Assistant Lecturer
Siberian State Technological University

September 2000 – August 2003 (3 years). Krasnoyarsk, Russia.

Lectured on information sciences, databases, structural and object-oriented programming for software engineering students.


Master’s Degree, Computer Science
Majored in Distributed Automated Systems.
Siberian State Technological University
2000 – 2002

Bachelor’s Degree, Computer Science
Siberian State Technological University
1996 – 2000