Krzysztof Sliwinski
Full-stack developer and infrastructure engineer
Crystal Lake, IL, open to remote krzysztof.oddologyinc.com linkedin.com/in/krzysztof-m-sliwinski github.com/WedrownyElite
Summary
I'm a developer who builds production systems and then keeps them running. I built and run a SaaS platform and client portal that paying clients use, a Flutter app that's live on Google Play, and the Linux servers they all run on, with automatic failover, off-site backups and ongoing security work. I've also worked in enterprise IT on identity management, endpoint administration and high-volume ticket queues. I'm looking for IT engineering, backend or security-focused developer roles.
Skills
- Development
- JavaScript and TypeScript (Node.js, Express, React), Flutter and Dart, Java, Python, C++, C#, SQL, REST APIs, Git, AI tools
- Infrastructure
- Linux (Ubuntu) administration, Apache, PM2, systemd, Let's Encrypt, Cloudflare DNS, failover and backup design, SSH hardening, firewalls
- Security
- Access control reviews, credential storage (hashing, encryption at rest, 2FA), input validation, privacy masking, penetration testing fundamentals
- IT and identity
- Active Directory, Okta, Microsoft 365 and Exchange, ServiceNow, Kaseya, imaging and deployment, Windows 10 and 11
- Languages
- English (fluent), Polish (conversational)
Experience
Oddology LLC, Co-founder and full-stack developer
2023 to present, remote- Built and run the company platform (Node.js, Express, React, SQLite) for clients, projects, contracts, Stripe billing and websites, plus a client portal on the same backend that paying clients use.
- Added permission groups that apply to signed-in sessions almost in real time across a multi-tenant setup, and consent-aware analytics with PDF and XLSX export.
- Run the Linux servers the company and its clients depend on: a primary and a hot standby with automatic failover (about 42 seconds in a real test), syncs every few minutes, nightly off-site backups and monitoring.
- Found and fixed security problems: a client portal access-control audit, encrypted 2FA secrets and stronger password hashing (tested, rolling out), path validation and visitor IP masking. Each fix has tests and a rollback I practiced first.
- Lead developer on FieldLedger (React, TypeScript, Express, Drizzle, SQLite), which replaced a client's 50-tab Excel workbook with invoicing, payroll and reporting. Launched April 2026.
- Designed and built client websites with SEO, schema markup and ad campaigns, plus custom backends when a client needed one.
Power Construction LLC, Windows upgrade technician (contract via Aline Consulting)
Sep 2025 to Oct 2025, Chicago, IL- Upgraded 120+ employees from Windows 10 to Windows 11 in a one-month contract.
- Imaged and set up devices, troubleshot problems and got assets ready.
AIT Worldwide Logistics, IT technician I (contract via LaSalle Network)
Oct 2024 to Feb 2025, Palatine, IL- Helped bring a ServiceNow queue that grew after an acquisition from the low thousands down to under 100 open items, closing 400 to 500 a month.
- Set up and removed user accounts across Active Directory, Okta, Microsoft 365 and Exchange with clean audit trails, and managed distribution lists, shared mailboxes and file-share permissions.
- Imaged and deployed laptops across U.S. locations during a major acquisition, and helped with the Windows 10 to 11 migration through Kaseya.
Other work
2023 to 2025The Home Depot, special services associate (part-time, 2025). Bath and Body Works, store associate (2024 to 2025). CVS Pharmacy, front store associate (2023), twice Employee of the Week.
Projects
LifeLogr, solo mobile developer
2024 to present- Flutter and Firebase health tracker in production on Google Play, covering food and macros, barcode scanning, AI that reads nutrition labels from photos, workouts, sleep, weight, journaling, pantry and groceries.
- Notifications that adapt to what each user logs, and a self-hosted media server mirrored to a standby.
Feudline, game server developer
Independent- One Java plugin, 200+ classes and about 45,000 lines, that runs a Minecraft factions server: 20+ gameplay systems, an inventory GUI framework and live config reloads.