Pavlos Kallis

Pavlos Kallis

Software Architect
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I have more than 7 years of experience as a software engineer, 4 years as a lead developer / architect and more than 5 years of experience in the Python language.
My experience comes mainly from fast-paced startups where I have collaborated directly with C-level executives.
I have led small teams, architected and built products and systems from ground zero.

Work Experiences

Senior Software Engineer, Backend

Douleutaras (Remote) | May 2021 - Present
  • Responsible for technology/architecture aspects of the backend
  • Major performance optimizations in the database (PostgreSQL) and the HTTP API (Django Rest Framework)
  • Gitlab CI pipeline optimizations
  • Migration of static assets and media to S3
  • Celery task optimizations

Senior Software Engineer, Backend and Team Leader

Centaur Analytics | Jan 2017 - Mar 2021
  • Led a team of 3 engineers / data scientists, responsible for architecture, design, code quality, code reviews, and system stability
  • Architected, implemented, and maintained all Python microservices in Centaur's codebase, including the infrastructure (3 dockerized microservices running on Kubernetes and AWS, about 50K lines of code)
  • Executed major performance optimizations of CPU-intensive tasks
  • Introduced new technologies to Centaur's technology stack (Machine learning, Python, Docker Swarm, GRPC, User Analytics tools)
  • Architected/Built a production-grade data pipeline to handle time series data
  • Architected/Built a computational fluid dynamics system which required knowledge of threads, os processes, filesystem, and memory management
  • Architected/Built a computer vision system on top of Tensorflow running on AWS aimed to detect images/number of pests
  • Implemented techniques to evaluate accuracy of classification algorithms
  • Time series preprocessing, classification and forecasting

Technologies: Python, Flask, Celery, Scikit-learn, Pandas, Numpy, Scipy, Keras, Tensorflow, RabbitMQ, MongoDB, AWS, Docker, Docker Swarm, NodeJS, Unix, Git

Senior Software Engineer

Centaur Analytics | Oct 2016 - Dec 2016

Co-founder and software engineer

Testributor (Remote) | Nov 2015 - Sep 2016

Active feature development and creation of business plan. My code contributions are on Github

Technologies: Ruby, Ruby on Rails (4+), NodeJS, PostgreSQL, Redis, Docker, Docker Compose, AWS, Heroku, Git

Software Engineer

KEPYES (Greek Army) | Mar 2016 - Aug 2016

As part of my mandatory military service, I developed web application software according to ISO 27001 standards handling top-secret information

Technologies used: Javascript, MySQL, HTML5, CSS3, PHP, laravel

Software Engineer

Incrediblue | Oct 2013 - Oct 2015
  • Implemented core features of the product (messaging system, search)
  • Implemented analytics infrastructure (mixpanel, tag manager, google analytics)
  • Setup Javascript testing infrastructure ( Teaspoon, Jasmine )

Technologies: Ruby on Rails, Git, PostgreSQL, TDD, BDD, Javascript

Internship

CERTH | Jul 2013 - Sep 2013

Implementation of a network testbed administration tool

Technologies: PHP, Javascript

Projects

Testributor

Open Source

As co-founder of Testributor, I played a crucial role in shaping our product and improving the overall user experience.

Collaborating and building a product in a remote-first manner was a challenging, nevertheless an invaluable experience. Apart from software development, I got involved with customer acquisition, customer development and other aspects of a business plan.

PDMongo

Open Source

PDMongo is a python package designed to integrate painlessly Pandas dataframes with MongoDB

I created this package because it was very difficult to read collections from MongoDB and convert them to a pandas dataframe so that they can be used for data analysis.