Mike S.

Mike S.

Full Stack Engineer

Berlin, Germany
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About Me

Mike is a seasoned full-stack developer and software architect with in-depth knowledge of Node.js, Ruby on Rails, and React. He has a unique ability of understanding and translating business requirements into development roadmaps. In his previous roles as a team lead and CTO, he has developed strong project management and communication skills.

Full-stack Web Development Back-end Development IT Project Management Web Scraping CTO SQL ANSI SQL REST APIs CSS Github RSpec Ruby on Rails (RoR) Ruby PostgreSQL

Work history

Senior Software Developer
2021 - 2022 (1 year)
  • Scaled a centralized package tracking system to process 160 million shipments and 2+ billion status updates per month.

  • Collaborated with external partners, such as UPS, DHL, and Parcel Perform, designing and building state-of-the-art integrations. This work led to much higher throughput, lower latencies, and cost savings of $500,000 per year.

  • Mentored junior engineers through pair programming and code reviews, involving them in higher-level technical design work and department-wide show and tells. Helped build promotion case from an intern to the developer, skipping the junior level.

RubyRuby on Rails (RoR) Apache Kafka React MySQLScaling Performance Technical Design Technical Leadership Hiring Interviewing GraphqlSoftware ArchitectureeCommerce ShopifyTechnical Architecture LeadershipFull-stack Project ManagementGithubWeb ScrapingPythonHTMLAPI IntegrationRSpecActiveAdmin REST
Fortune 500 Manufacturing Company
Senior Software Engineer
2019 - 2020 (1 year)
  • Created a library of reusable React components, including documented use cases in Storybooks and tests in Jest/Enzyme.

  • Implemented ARIA landmark 1 accessibility requirements.

  • Upgraded an existing data API service from Rails 4 to Rails 6.

  • Implemented new data API endpoints, focusing on speed, caching, and data structure tailored for the presentation layer.

  • Migrated legacy local websites into a single multilingual site.

  • Lowered the cost of feature development, improved delivery times, largely removed QA issues on new pages, and improved site performance.

RubyCSSREST APIs Back-end Development PostgreSQLJavaScriptAmazon Web Services (AWS) Dynamics CRM 365 DockerEnzymeJestStorybookRuby on Rails (RoR) React Web DevelopmentSoftware ArchitectureJIRAArchitecture APIsTechnical Leadership Technical Architecture LeadershipFull-stack Project ManagementGithubHTMLAPI IntegrationRSpecActiveAdmin REST
Prodigy Finance
Senior Software Engineer
2018 - 2019 (1 year)
  • Prepared architectural outline and led implementation of an OAuth OpenID Connect provider, enabling single-sign-on (SSO) to all Prodigy services.

  • Migrated existing services from EC2 to ECS Fargate, enabling autoscaling, blue-green deploys, and improving security.

  • Reimplemented existing Excel cash flow models as a Ruby on Rails and React application, lowering turnaround time for new models from days to minutes.

React RubyCSSREST APIs Back-end Development PostgreSQLJavaScriptFinancial Data OpenID Connect (OIDC) Amazon Web Services (AWS) PythonOpenAPI OAuthDockerRuby on Rails (RoR) Web DevelopmentSoftware ArchitectureArchitecture APIsSlackAsanaTeam Leadership Technical Leadership Technical Architecture LeadershipFull-stack Project ManagementGithubHTMLAPI IntegrationRSpecREST
2014 - 2017 (3 years)
  • Developed a tool indexing more than 30 million unique YouTube channels weekly, using a mix of API access and scraping.

  • Rebuilt a legacy jQuery front end in React from scratch for both Stagelink customer-facing products; moved away from a monolithic Rails app towards API-based services.

  • Implemented and optimized a show-attendance prediction algorithm designed by the company's CEO. Deployed the new code to production—increasing prediction accuracy by 15% and increasing the calculation speed three-fold.

  • Hired and led a team of six developers—performing code reviews and training sessions, having one-on-one meetings every two weeks, and mentoring junior developers.

  • Designed a voting fraud detection system that analyzed tens of thousands of votes per day to identify fake users, multiple votes by the same person, and other abuses.

  • Implemented an extensible payment back end, interfacing with multiple payment providers, including PAYMILL, Stripe, PayPal, SOFORT, and Wirecard.

CTO Facebook Open Graph API CSSREST APIs Back-end Development Pipedrive APIWeb ScrapingAmazon Web Services (AWS) PostgreSQLElasticsearch ReduxReact JavaScriptRuby on Rails (RoR) RubyWeb DevelopmentSoftware ArchitectureArchitecture APIsSlackAsanaTeam Leadership Technical Leadership SendGridSendGrid API Technical Architecture React NativeLeadershipFull-stack Project ManagementBitbucketHTMLAPI IntegrationBrainTree HerokuRSpecActiveAdmin Payment APIs REST
Digital Polsat
Software Engineer
2012 - 2013 (1 year)
  • Developed a search engine for a music-streaming platform consisting of more than 15 million songs. The search engine was based on Elasticsearch and MongoDB and was deployed to a cluster of EC2 servers.

  • Finetuned a search engine configuration based on artist popularity and measurements of hit/miss ratio for presented results.

  • Exposed the search engine to mobile, web, and desktop applications by building a JSON-based API service in Rails.

  • Implemented a recommendation service based on user preferences, content team picks, etc.

  • Developed a caching-layer based on Memcached (for in-app caching) and Varnish (for page and endpoint-level caching).

Facebook Open Graph API CSSBack-end Development PostgreSQLJavaScriptAmazon Web Services (AWS) Elasticsearch MongoDBRuby on Rails (RoR) RubyWeb DevelopmentAPIsFull-stack HTMLAPI IntegrationHerokuREST
Full-stack Developer
2010 - 2011 (1 year)
  • Integrated LiveChat with various third-party applications including Zendesk, Salesforce, Highrise, and Zoho to pull customer data into a chat window.

  • Built an outside-facing REST API, wrote docs and sample code, helped outside developers integrate with it, and troubleshot issues.

  • Created chat plugins for popular eCommerce solutions (Shopify, Magento, WooCommerce, and the like).

  • Developed a wizard allowing LiveChat clients to customize their chat experiences for their users by changing the color scheme for the chat window, adding pre-chat questions, and a post-chat survey.

  • Built an API for an internal dashboard showing sales and usage statistics.

CSSREST APIs Back-end Development JavaScriptRESTful Development MySQLjQueryPHPWeb DevelopmentAPIsFull-stack HTMLAPI IntegrationREST
Software Developer
2009 - 2010 (1 year)
  • Designed and implemented a quality assurance application—including a dynamic survey generator and HTML5 audio player. I also developed a back-end service that selected a random sample from a pool of all sales calls recorded on a previous day.

  • Wrote, specified, designed, and developed an applicant-tracking system according to HR department requirements.

  • Migrated the internal apps from a legacy homegrown PHP framework to Symfony.

Market Research Company
Project Leader
Present (2024 years)
  • Gathered business requirements and provided timeline and technical architecture of the project.

  • Built a distributed, queue-based, horizontally scaling scraper in Node.js, deployed to ECS.

  • Integrated residential IP address proxy and CAPTCHA solving service.

  • Implemented the ETL process, ingesting data from Alibaba, AliExpress, Taobao, and Tmall.

  • Built the React front end, allowing data filtering, data export, and scraping progress monitoring.

CSSREST APIs Back-end Development PostgreSQLJavaScriptAmazon Web Services (AWS) Amazon Elastic Container Service (Amazon ECS) Project ManagementWeb ScrapingReact Express.js Node.jsETLWeb DevelopmentSoftware ArchitectureArchitecture APIsTeam Leadership Technical Leadership LeadershipFull-stack BitbucketHTMLAPI IntegrationHerokuRSpecREST


Stack Overflow

With over 250 answers and more than 8,600 points, I'm in the top 5% of Stack Overflow users overall.


Being the CTO, I was responsible for all sorts of things at Stagelink. In the day-to-day work, I was coding and managing a team, occasionally jumping into server and AWS administration, developing product roadmaps and writing specifications, performing code reviews and one-on-ones with developers, negotiating with designers, and so on. The things that I'm most proud of: • We went through two major redesigns of the website while improving usability, performance, the looks, and user satisfaction. • I successfully moved away from the monolithic Rails app towards an API—cleanly separating the front-end from back-end with some background services performing the heavy lifting (like emails, and so on). • I made the right technical decisions by separating different parts of the product codebase and making them communicate via an API. This saved us from many headaches when scaling-up. • I helped new developers quickly get proficient with Stagelink's code and systems—to decrease the bus factor.

Pipedrive Gem

Pipedrive is a type of CRM software, and we used it a lot at Stagelink to track our sales efforts. Based on the YouTube scraping results, we were sending cold emails to matching artists and tracked the progress in Pipedrive.We started to use a gem to make our lives easier, but the code was pretty terrible. In my free time, I started refactoring it and bringing the quality (and code coverage) up a bit—we are planning to release a new version at some point.Work Done:• Removed recursion from the paging-handling code.• Moved the HTTP calls out of the data objects.• Performed general cleanup of the code.• Updated the dependencies and made it work with the current Ruby versions.


Master of Science Degree in Computer Science
Wrocław University of Science and Technology
2006 - 2011 (5 years)