Jan Grzesik, Developer in Kraków, Poland
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Jan Grzesik

Verified Expert  in Engineering

Bio

Jan is a full-stack developer and a product engineer with more than five years of experience building SaaS applications. Building applications for developers is his particular interest. Jan has built a web-based IDE at Estimote (YC alumni) and is currently working on a next-gen E2E monitoring tool at Checkly. He likes to use React, Vue.js, Node.js, PostgreSQL, Redis, Docker, Heroku, AWS, and Serverless.

Portfolio

Checkly
Amazon Web Services (AWS), AWS Lambda, Node.js, Vue, PostgreSQL, Stripe
Estimote
Heroku, PostgreSQL, Express.js, Node.js, React
VMLY&R Poland
Public Health, Apache ZooKeeper, Elasticsearch, RabbitMQ, React, MongoDB...

Experience

  • JavaScript - 6 years
  • Express.js - 5 years
  • Node.js - 5 years
  • Redis - 5 years
  • PostgreSQL - 4 years
  • React - 4 years
  • Amazon Web Services (AWS) - 3 years
  • MongoDB - 2 years

Availability

Part-time

Preferred Environment

Amazon Web Services (AWS), Node.js, Heroku, PostgreSQL, Redis, React, Vue, Serverless, JavaScript, TypeScript

The most amazing...

...side project I've completed is a real-time distributed file system synchronization tool (rsync clone built with TypeScript).

Work Experience

Senior Full-stack Developer

2020 - PRESENT
Checkly
  • Created a serverless module for executing untrusted (user-submitted) Microsoft Playwright scripts.
  • Rewrote the core of the SaaS subscription system to a metered billing.
  • Worked on integrations, reliability, and improving code readability.
Technologies: Amazon Web Services (AWS), AWS Lambda, Node.js, Vue, PostgreSQL, Stripe

Senior Full-stack Software Engineer

2017 - 2020
Estimote
  • Introduced a real-time analytics system for millions of events per day which improved the build and test pipelines.
  • Built a web-based IDE for managing IoT devices (https://www.youtube.com/watch?v=UvTvzO5YstQ).
  • Oversaw product development, parts of marketing, and software architecture of an IoT prototyping platform.
Technologies: Heroku, PostgreSQL, Express.js, Node.js, React

Software Engineer

2016 - 2017
VMLY&R Poland
  • Worked on a mature SaaS product that provides real-time marketing insights from social media.
  • Designed and implemented an analytics computation engine that combines 50 different metrics from a half dozen external providers.
  • Worked on a web dashboard with interactive charts, using React and Highcharts.
  • Performed integrations with external APIs. Built a real-time integration monitoring tool.
  • Improved the CI build performance by 300% running extensive unit and integration tests.
Technologies: Public Health, Apache ZooKeeper, Elasticsearch, RabbitMQ, React, MongoDB, Node.js

Junior Software Developer

2015 - 2016
DreamLab
  • Designed and created a web application with OAuth, AngularJS, D3.js, and Tornado for internal workflow management.
  • Created an API for mobile devices that serves millions of devices per day, for the newspaper Blic.rs (Node.js, Express, JSON-RPC, Jasmine).
  • Delivered the project with high unit-test coverage.
  • Worked extensively with international customers and developers.
  • Developed in the largest private cloud environment in Poland.
  • Used continuous integration tools.
  • Communicated in English on a daily basis in a Scrum team with remote coworkers.
Technologies: PostgreSQL, AngularJS, Tornado, Python, Node.js

Experience

Session Service

A simple authentication service with register, login, and logout actions. In this sample, authentication is token-based, and sessions are stored as documents in MongoDB. The code is written in TypeScript. It is part of a back-end Express-based application.

Syncrow

https://github.com/jan-osch/syncrow
A real-time file system synchronization tool. Created with TypeScript and Node.js, using a core Sockets library. It provides authentication, initial synchronization strategies, and ignores specific paths features.

Personal Landing Page

Personal landing page created with Next.js hosted on Vercel includes optimizations that allowed me to achieve very high lighthouse scores (the lowest 96%). Additionally, I have set up E2E Monitoring to detect degradations and errors.

Education

2015 - 2019

Master's Degree in Computer Science

Jagiellonian University - Kraków, Poland

Skills

Libraries/APIs

React, Node.js, Sinon.JS, Highcharts, Vue, Stripe, Sockets, Bacon.js

Tools

Mocha, WebStorm, Bitbucket, Robo 3T (Robomongo), RabbitMQ, Apache ZooKeeper, Git, Photoshop CS6

Languages

JavaScript, Python 3, TypeScript 2, Python, TypeScript, Java 8, Bash

Frameworks

Express.js, Chrome, AngularJS, Next.js, Hapi.js

Platforms

MacOS, Unix, Heroku, AWS Lambda, Amazon Web Services (AWS), Linux

Storage

PostgreSQL, Redis, Elasticsearch, MongoDB

Paradigms

Microservices, Functional Programming

Other

Tornado, Public Health, Serverless

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