Jan Szumiec - Staff Software Engineer

Q: Where is Jan based?

Jan is based in Warsaw, Poland .

Q: What languages does Jan speak?

Jan speaks the following languages: English (Native), Polish (Native) .

Q: How many years of experience does Jan have?

Jan has at least 18 years of experience. During this time, Jan has worked in at least 16 different roles and for 18 different companies . The average length of individual experience is 1 year and 11 months . Note that Jan may not have shared all experience and actually has more experience.

Q: What is Jan's latest experience?

Jan's most recent position is Staff Software Engineer at Deliveroo .

Q: What companies has Jan worked for in recent years?

In recent years, Jan has worked for Deliveroo , Indeed Flex , Knowde , and PixelPaper .

Q: Which industries is Jan most experienced in?

Jan is most experienced in industries like Information Technology , Professional Services , and Banking and Finance . Jan also has some experience in Food and Beverage , Metals and Mining , and Government and Administration .

Q: Which business areas is Jan most experienced in?

Jan is most experienced in business areas like Information Technology , Product Development , and Project Management . Jan also has some experience in Business Intelligence , Sales , and Operations .

Q: Which industries has Jan worked in recently?

Jan has recently worked in industries like Information Technology , Food and Beverage , and Education .

Q: Which business areas has Jan worked in recently?

Jan has recently worked in business areas like Information Technology , Product Development , and Project Management .

Recommended expert

Warsaw, Poland

Experience

Jul 2024 - Apr 2025

10 months

Staff Software Engineer

Deliveroo

Extended an existing system for propagation of marketing events to send data to TikTok which allowed us to use a new remarketing channel.
Unlocked additional 10% remarketing channel utilization by performing detailed analyses on missing or invalid data in events.
Created a real-time pipeline for analysing event volumes against changes in application code, letting us roll back defective changes quickly.

Nov 2023 - Jul 2024

9 months

Staff Software Engineer

Indeed Flex

Maintained and added features to a large (850kLOC) Rails codebase of very high domain complexity.
Delivered a revamp of rate calculation required to onboard a £MM customer.
Delivered a feature to enable granular shift edits unlocking £MMM in TAM.
Reduced time to diagnose problems by leveraging observability.

Jul 2022 - Oct 2023

1 year 4 months

Remote

Engineering Manager

Knowde

Managed and led international teams working remotely from multiple timezones.
Delivered key projects despite technical and non-technical obstacles.
Introduced service observability to the organization, simplified access control architecture, led initiatives to reduce tech debt.
Reduced the load on a key application by 95%. Saved $18k p/a in the first 8 weeks, saved an additional $25k p/a in 2023.
Introduced an incident response process, and a technical debt management process.

Apr 2021 - Jun 2023

2 years 3 months

Co-Founder

PixelPaper

Rolled out a production-ready collaborative, embeddable whiteboard solution for the EdTech market in 90 days.
Sales calls, discovery meetings, architecture, implementation and some project management.
Profitable, but not enough to keep it alive.

Dec 2020 - Jul 2022

1 year 8 months

London, United Kingdom

Senior Software Engineer - Network Economics (contract)

Deliveroo

Rolled out an internal tool permitting non-tech staff to make changes to ML models, reducing time from 1+ days to a few minutes (Ruby).
Implemented and rolled out a key high-traffic (400M req/mo) service as an extraction from a monolith, to enable experimentation and improve CX (Go).
Assisted in resolving SEV-1 incidents. Caused a SEV-1 incident during load testing, recovered with minimal impact and introduced fixes.

Feb 2020 - Dec 2020

11 months

London, United Kingdom

Lead Product Engineer (contract)

Account Technologies Group

Architected and developed a new P2P investment product in 6 months from inception to market.
Through Vestapay, dramatically lowered the cost of capital for complementary products (Tappily & SafetyNet).
Architected and developed a new platform for the real estate sector including PSD2 PISP/AISP integration.
Dramatically increased operational flexibility and lowered cost by leveraging cloud computing.
Pioneered identity pinning and leveraged social logins through the use of an IAM platform.
Taught the team practices around product development, such as user research, rapid prototyping and dealing with continuously changing requirements.
Mentored a team of 4 junior developers.

Oct 2019 - Jan 2020

4 months

London, United Kingdom

Technical Architect (contract)

Department for Education

Conducted market and technical research in the domain of F&A management software as part of an alpha-phase project in the fostering and adoption space.
Uncovered a dysfunctional ecosystem with very limited competition.
Formulated the department’s strategy to enter the market as a player and demonstrate what value for money looks like.

May 2017 - Sep 2019

2 years 5 months

London, United Kingdom

Engineering Lead, Blockchain (contract)

Boston Consulting Group/De Beers Group of Companies

Served as a technical leader during the inception phase of the project with Boston Consulting Group.
Developed a PoC for confidential data sharing using Intel SGX technology (C++, later Rust). Worked on code, architecture and devops (AWS, Rancher, Terraform).
Moved with the project when it was handed over to the client and served as an interim CTO. Reported directly to the general manager.
Regularly presented to the board of the De Beers Group.
Built a team of 7 developers, defined roadmaps, managed risk and technical debt.

Nov 2016 - May 2017

7 months

London, United Kingdom

Software/Infrastructure Engineer (contract)

Open Banking UK

Co-authored the UK Open Banking API standard.
Attended meetings with stakeholders (CMA9 banks), authored technical recommendations.
Built performance tracking dashboards to ensure NFR compliance (Go + Lambda).

May 2015 - May 2016

1 year 1 month

London, United Kingdom

Lead Software Engineer (contract)

PrimeRevenue

Designed and implemented a package for managing the lifecycle of corporate bonds using Rails and React.js.
Acted as the tech-person-in-charge in a small team of 4 SVPs.

May 2013 - May 2015

2 years 1 month

London, United Kingdom

Senior Software Engineer/Tech Lead (contract)

UK Ministry of Justice

Delivered the Prison Visits Booking digital exemplar, a flagship project for the UK government.
Adopted a user-centric approach, conducted user research and usability testing with end users, resulting in a product with 99% user satisfaction.
Introduced a performance tracking framework to identify adopters and laggards through a public dashboard.
Reallocated 35 FTEs resulting in savings of £11M over 5 years.
Participated in discovery for Money to Prisoners, delivering £50M of savings by end-to-end automation, reallocating 65 FTEs and eliminating postal money orders in favour of bank transfers.

Feb 2013 - May 2013

4 months

London, United Kingdom

Senior Software Engineer (contract)

wearefriday.com

Rectified architecture and implementation of a CMS and IAM system for a major bank.
Eliminated unnecessary microservices by reincorporating functionality into a modular monolith.
Eliminated bottlenecks in sign-on system by replacing home-brew crypto with efficient and secure constructs.

Mar 2012 - Feb 2013

1 year

London, United Kingdom

Software Engineer (backend)

STATE

Built a hypedmedia API for a social network around opinions using Ruby, Node.js and MongoDB.
Reimplemented data import infrastructure for tens of GBs of TSVs into MongoDB.

Dec 2011 - Mar 2012

4 months

Kraków, Poland

Software Engineer

Sherman’s Travel Media

Rebuilt a medium-size (250k daily visits) customer facing application in Ruby/Rails.
Improved performance, reliability and testability.

Apr 2010 - Dec 2011

1 year 9 months

Kraków, Poland

Co-Founder & CTO

Sentymetr

Identified a market need for social media monitoring in the Polish market.
Designed and implemented a data collection infrastructure in Ruby (web scraping, API integrations).
Implemented an ML algorithm for sentiment analysis based on Vowpal Wabbit.
Achieved product-market fit but failed at sales and eventually ran out of funds.

Jun 2009 - Jun 2011

2 years 1 month

Kraków, Poland

Co-Founder & CTO

Shopmaster

Identified a market need for a simple, hosted e-commerce platform with easy payment integration.
Ran the project with a team of 2 developers, customizing Spree (an open source e-commerce platform).
Implemented a universal shopping cart allowing drop-in integration of e-commerce features into existing webpages.
Achieved near product-market fit but ran out of funds.

Nov 2007 - Feb 2008

4 months

Mountain View, United States

Software Engineer (Intern)

Google, Inc.

Performance-tuned Google Calendar, a large (1.5MB uncompressed JS) single page application.
Implemented a system for dynamically loading dependencies on demand to reduce page load time, saving 15% on initial page load.
Worked on integrating holiday calendars with Google Calendar.

Oct 2006 - Jun 2009

2 years 9 months

Kraków, Poland

Co-Founder & CTO

Infinite Loop

Started a software house specializing in Ruby/Rails development, one of the first in Poland.
Worked with Audible GmbH developing a product that ultimately became Amazon ACX post-acquisition.
Built a team of 15 developers and served as CTO, PM and Software Engineer.
Learned critical lessons on how to and how not to run a company.

Jun 2006 - Aug 2006

3 months

London, United Kingdom

Software Developer (Intern)

Resolver Systems

Worked in a team practicing Extreme Programming by the book.
Participated in building the largest IronPython project at the time, a programmable spreadsheet program (Resolver One).
Implemented network-shareable worksheets and learned about distributed system failures.

Industry Experience

See where this freelancer has spent most of their professional time.

Experienced in Information Technology, Professional Services, Food and Beverage, Banking and Finance, Government and Administration, and Metals and Mining.

Information Technology

Professional Services

Food and Beverage

Banking and Finance

Government and Administration

Metals and Mining

Business Area Experience

See which departments and functions this freelancer has contributed to most.

Experienced in Information Technology, Product Development, Project Management, Business Intelligence, Sales, and Research and Development.

Information Technology

Product Development

Project Management

Business Intelligence

Sales

Research and Development

Summary

Seeking new challenges at a company where I can make a difference, working with creative and interesting people and build great products.

Skills

Programming: Ruby, Python, C, Go, Rust, Javascript
Database: Postgresql, Redis, Kafka, Mongodb, Sqlite
Other: Varnish, Grpc, Terraform, Cdb
Iam: Oauth/openid Connect, Saml
Operating Systems: Macos X, Linux, Freebsd
Concepts: Test-driven Development, Xp, Mvc, Ddd, Cqrs/es, Microservices, Rest, Rpc
Devops: Ansible, Docker, Terraform, Aws, Rancher
Cryptography: Symmetric And Asymmetric Encryption, Digital Signatures, Macs, Pki, Hsms

Languages

English

Native

Polish

Native

Education

Oct 2002 - Jun 2007

Politechnika Krakowska

Master of Science in Computer Science · Computer Science · Kraków, Poland

Statistics

Experience

Total positions 19

Experience in Information Technology 11 y

Avg length 1 y 2 m

Longest experience 2 y 8 m

Global Experience

Countries worked in 3 (United Kingdom, Poland, United States)

Primary country United Kingdom

Expertise

Recent roles Staff Software Engineer, Engineering Manager, Co-Founder

Main industries Information Technology, Professional Services, Food and Beverage

Main business areas Information Technology, Product Development, Project Management

Qualifications

Highest degree Master

Profile

Created

March 2026

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Frequently asked questions

Do you have questions? Here you can find further information.

Where is Jan based?

Jan is based in Warsaw, Poland.

What languages does Jan speak?

Jan speaks the following languages: English (Native), Polish (Native).

How many years of experience does Jan have?

Jan has at least 18 years of experience. During this time, Jan has worked in at least 16 different roles and for 18 different companies. The average length of individual experience is 1 year and 11 months. Note that Jan may not have shared all experience and actually has more experience.

What roles would Jan be best suited for?

Based on recent experience, Jan would be well-suited for roles such as: Staff Software Engineer, Engineering Manager, Co-Founder.

What is Jan's latest experience?

Jan's most recent position is Staff Software Engineer at Deliveroo.

What companies has Jan worked for in recent years?

In recent years, Jan has worked for Deliveroo, Indeed Flex, Knowde, and PixelPaper.

Which industries is Jan most experienced in?

Jan is most experienced in industries like Information Technology, Professional Services, and Banking and Finance. Jan also has some experience in Food and Beverage, Metals and Mining, and Government and Administration.

Which business areas is Jan most experienced in?

Jan is most experienced in business areas like Information Technology, Product Development, and Project Management. Jan also has some experience in Business Intelligence, Sales, and Operations.